Key wordsBone neoplasms, dental tissue neoplasms, jaw neoplasms, jaw neoplasms, osteogenic sarcoma, chondrosarcoma
Bone consists of a solid mineral phase and a matrix of osteoid phase that contains osteoclasts (bone-resorbing cells), osteoblasts (bone-forming cells), and osteocytes (osteoblasts that become incorporated into the matrix). Although bone tumors are rare in the head and neck region, they span a wide spectrum of neoplasms. Primary bone tumors arise from either cellular matrix or lymphoreticular and myeloid cells in the marrow spaces. Occasionally, embryonic sequestered elements also may be the source for a primary neoplasm (e.g., salivary rests giving rise to “central” salivary neoplasms in the mandible or maxilla). Neoplasms also may arise from odontogenic elements in the maxilla and mandible. Generalized disorders of bone turnover and remodeling such as Paget’s disease also may increase the risk of development of malignant tumors within the involved bones. Exposure to ionizing radiation, particularly at a young age (e.g., in children with a retinoblastoma) significantly increases the risk of the subsequent development of malignancy, such as osteosarcoma. Metastatic tumors from other sites also can present in the craniofacial skeleton.
Primary benign neoplasms of the craniofacial skeleton consist of osteomas, osteochondromas, and osteofibromas. Occasionally, benign tumors of vascular origin such as hemangiomas are also seen in the craniofacial skeleton. These are often asymptomatic and found incidentally. However, the most common benign bony lesions in the head and neck region are developmental malformations at the site of embryonic fusion lines, such as the torus palatinus. Osteomas typically are asymptomatic and may arise on the calvarium and in the paranasal sinuses. Osteomas usually appear after puberty and require intervention only if they are symptomatic. Malignant transformation is uncommon but occasionally may be associated with Gardner syndrome. Osteoid osteomas (ivory osteomas) are smaller lesions, whereas osteoblastomas are thought to be their larger, more aggressive counterparts. Osteoid osteomas typically present in children and young adults, are usually solitary, and are associated with pain that may be out of proportion to size. Local excision is adequate treatment. In contrast, osteoblastomas are rarely painful, involve long bones, and have a small tendency to progress to an osteosarcoma.
Benign tumors of cartilaginous origin include osteochondromas, chondromas, chondroblastomas, and chondromyxoid fibromas. Osteochondromas (exostoses) are benign, cartilage-capped, bony outgrowths. These tumors usually are solitary but can be multifocal in patients with familial osteochondromatosis. Solitary lesions usually involve the mandible or skull base. Chondromas (enchondromas) are tumors of the hyaline cartilage that frequently arise within the bone. They are thought to be derived from remnants of epiphyseal cartilage. These tumors usually are solitary but can be multiple in persons with Ollier disease (enchondromatosis), which is a nonhereditary spontaneous disorder. A familial variant also exists (Maffucci syndrome) in which chondromas occur in conjunction with cutaneous hemangiomas. Although solitary tumors have very low risk for malignant transformation, multiple, familial tumors progress to chondrosarcomas in up to 50% of cases.
Chondroblastomas usually arise along the epiphyseal region of long bones. Although rare in the head and neck skeleton, they may occur in the temporal bone, mandible, or parietal bone. These lesions are histologically benign and may have radiologic features similar to those of malignant lesions. Chondromyxoid fibromas typically involve long bones but may arise in the mandible, although this presentation occurs rarely. These lesions are benign and require surgical intervention only if they are symptomatic.
Cystic lesions of the bone are common in the head and neck region and most frequently are of odontogenic origin. Nonodontogenic bony cysts typically are fissural cysts that may be lateral (nasolabial or globulomaxillary), medial (nasopalatine or median palatal), or median mandibular ( Fig. 16.1 ). Nasolabial cysts (Klestadt cysts) arise from epithelial rests remaining from the “fusion” of the glabellar process with the lateral nasal process and the maxillary process, or due to the persistence of epithelial remnants from the nasolacrimal duct extending between the lateral nasal process and the maxillary prominence. These lesions have a predilection for females (75%) and are found near the base of the nostril. They can be bilateral in up to 10% of cases.
Nasopalatine cysts are developmental lesions that are thought to arise from epithelial remnants of embryonic nasopalatine ducts within the incisive canal. They are the most common nonodontogenic cysts and have a predilection for males. Globulomaxillary cysts arise from epithelial elements trapped in the embryonic fusion line between the glabellar process of the frontonasal bone and the maxillary process of the palatine bone. Odontogenic cysts are thought to be derived from remnants of dental lamina or from enamel organ. They can be periodontal (apical, lateral, or residual), dentigerous, gingival, primordial, or keratinizing and calcifying ( Fig. 16.2 ). Periapical or radicular cysts account for more than 50% of cystic lesions. Radicular cysts are thought to arise from an inflammatory process of the epithelial cell rests of Malassez. Dentigerous cysts are developmental cysts that arise from the enamel or dental lamina of an unerupted tooth. They are epithelium-lined sacs that involve the crown of unerupted teeth. Dentigerous cysts arise most commonly from the third molars but also may arise from the bicuspid, cuspid, or canine teeth.
Gingival cysts that arise from remnants of the dental lamina are located in the corium below the surface epithelium. They typically present as multiple nodules on the alveolar ridges of newborn or young infants. These cysts generally are asymptomatic and usually resolve spontaneously. Lateral periodontal cysts generally arise from epithelial rests in the periodontal ligament. Primordial cysts develop in place of a tooth when the dental follicle undergoes cystic degeneration. They also may arise from a supernumerary tooth bud. The treatment is surgical enucleation or curettage with preservation of adjoining teeth.
In 2005, the World Health Organization (WHO) changed the terminology of the lesion previously referred to as odontogenic keratocyst (OKC) to calcifying cystic odontogenic tumor (CCOT). The rationale for the name change was genetic data demonstrating alterations in the PTCH1 gene and the potential for aggressive behavior of these lesions. However, the 2017 WHO classification reverts to the usage of the terminology “odontogenic keratocyst.” Furthermore, the 2017 WHO classification states that CCOT is now synonymous with “calcifying odontogenic cyst,” a simple cyst lined by an odontogenic ameloblastoma-like epithelium, with associated ghost cells. The rationale for these additional changes is unclear; however, it is important to understand that regardless of “terminology de jour,” this entity encompasses a spectrum of clinical behaviors. Odontogenic keratocysts most commonly involve the mandible in the region of the third molar and can extend into the ascending ramus. These lesions are distinguished from other odontogenic cysts by the presence of a keratinizing epithelial lining. They may vary from cystic to solid, and OKCs may involve the crown of a tooth but also can represent a keratinizing variant of the lateral periodontal cyst. Multifocal OKCs are associated with nevoid basal cell carcinoma syndrome. Small lesions may be effectively treated with enucleation. However, enucleation is inadequate for larger lesions with thin wall and satellite cysts. In the presence of multiple cystic lesions (osteitis fibrosa cystica), hyperparathyroidism should be ruled out.
Fibrous dysplasia is a rare, idiopathic primary bony lesion that is characterized by progressive replacement of medullary bone with proliferating, haphazardly arranged isomorphic fibrous tissue. Fibrous dysplasias can be monostotic (70%–75%) or polyostotic, which rarely can be associated with skin pigmentation and endocrine dysfunction (Albright syndrome). The head and neck region is not a common site for fibrous dysplasias (<1%), but when present, they most commonly involve the mandible, maxilla, frontal bone, or calvarium. These lesions tend to be progressive and cause symptoms by compression of local structures. Intervention is usually required to control symptoms or for cosmetic reasons. Less than 1% of these lesions may undergo malignant degeneration.
Giant cell tumors (GCT) of bone are lesions most commonly seen in long bones, but they also can occur in the head and neck region (e.g., in the temporal bone, sphenoid, and larynx). These tumors arise in young adults and have a locally aggressive course, with a high rate of recurrence after incomplete excision. A small proportion of these tumors undergo malignant degeneration and metastasize to distant sites. These tumors should be distinguished from giant cell reparative granulomas (epulis) that arise in the mandible and maxilla and have similar histopathologic features but no inherent malignant potential. In GCT, the giant cells overexpress the RANK receptor, a key mediator in osteoclastogenesis. Stromal cells secrete a cytokine RANKL, which stimulates the RANK receptor, contributing to bone resorption by the tumor. The United States Food and Drug Administration (FDA) has approved the use of Denosumab, a monoclonal antibody that specifically binds RANKL, preventing activation of RANK. This interaction, in turn, inhibits osteoclast formation, function, and survival, subsequently decreasing bone resorption. Currently, Denosumab is in use for inoperable or metastatic GCT, as well as neoadjuvant treatment before surgery. Further clinical trials are needed to establish optimal clinical utilization and long-term outcomes.
Ameloblastomas are the most common tumor arising from the odontogenic epithelium. They are seen most frequently in the mandible ( Fig. 16.3 ). The vast majority of these lesions are loculated, but they may present as a unicystic lesion, and rarely, they may be extraosseous in origin. The classic appearance of an ameloblastoma on a plain radiograph is that of a multiloculated, expansile lesion with a “soap-bubble appearance” ( Fig. 16.4 ). Although histologically benign, these tumors can be locally invasive. A small proportion of these tumors can degenerate into ameloblastic carcinomas. Small, benign ameloblastomas can be treated by enucleation, but this method is ineffective for larger lesions and results in a high rate of local recurrence. Multifocal recurrence with involvement of soft tissues may occur after inadequate initial treatment. For larger lesions of the mandible, segmental mandibulectomy is required for local control.
Primary malignant tumors of bone in the head and neck region are of osteogenic origin (osteosarcomas), chondrogenic origin (chondrosarcomas), hematopoietic origin (myelomas and lymphomas), or of unknown cellular origin (e.g., Ewing sarcomas, malignant giant cell tumors, and adamantinomas). Secondary involvement can occur from metastases from other sites.
The most common malignant tumor of the craniofacial skeleton is osteosarcoma, which may arise de novo (primary), in an area of a preexisting condition (e.g., fibrous dysplasia or Paget’s disease, or as a result of carcinogenic exposure [ionizing radiation]). Primary osteosarcomas generally develop in long bones in children and young adults ( Fig. 16.5 ). Head and neck involvement is less common (<10% of cases overall). The mandible followed by the maxilla is the most common site of involvement ( Fig. 16.6 ). Secondary osteosarcomas are seen most commonly in patients with Paget’s disease and retinoblastomas, but they also can occur in patients with Bloom, Li-Fraumeni, and Rothmund-Thomson syndromes. Exposure to external beam radiation is also associated with the development of osteosarcomas, especially in patients with inherited retinoblastomas. These tumors typically present as a mass lesion that may be painful.
Chondrosarcomas can occur de novo (in approximately 75% of cases) or in association with preexisting conditions such as multiple enchondromatosis (Maffucci or Ollier syndromes), exostoses, and rarely, chondroblastomas. Overall, these tumors involve the head and neck region in fewer than 10% of cases ( Fig. 16.7 ). The maxilla, cervical spine, and mandible are the most common sites for chondrosarcomas in the head and neck ( Fig. 16.8 ). The majority of patients present with a painless mass, and diagnosis is established by imaging or biopsy. Surgery is the mainstay of treatment for these neoplasms. Outcome generally is excellent and is dependent on the extent of disease at presentation, the tumor grade, and the completeness of resection. The histologic subtype also influences outcome, with the clear cell subtype (malignant chondroblastoma) having a better outcome than the myxoid, mesenchymal, or dedifferentiated subtypes.
Multiple myeloma and lymphoma arise from hematopoietic cells of the bone marrow and may present as solitary or multifocal bony lesions. Multiple myelomas often arise from a precursor condition (monoclonal gammaglobulinopathy of uncertain significance or smoldering myeloma). These tumors are of plasma cell origin and can be solitary (plasmacytoma) or widespread. Multiple myelomas cause systemic effects such as anemia and immunodeficiency because of progressive replacement of bone marrow with myeloma cells. Other symptoms arise from circulatory problems, renal dysfunction due to monoclonal gammaglobulinopathy, or hypercalcemia due to osteoclastic bone destruction. Multiple myeloma can be diagnosed by serum electrophoresis. Evaluation of the extent of disease requires imaging studies, bone marrow biopsy, peripheral blood counts, and renal function. Although plasmacytomas may benefit from surgery, curative treatment of multiple myeloma involves systemic chemotherapy and bone marrow transplantation.
Ewing sarcoma is a malignant round-cell tumor that shares a common translocation with peripheral primitive neuroectodermal tumors, and thus a continuum is considered to exist between these entities. The t(11;22)(q24;q12) translocation brings about fusion of the FLI1 gene on 11q24 and the EWS gene on 22q12. The presence of this translocation can be established by conventional cytogenetics or by molecular studies and is pathognomonic for these entities. These tumors typically arise from the pelvis, femur, humerus, and ribs; primary involvement of the head and neck region is seen in fewer than 5% of cases. The most common sites for Ewing sarcoma in the head and neck region are the calvarium and mandible. Extraosseous Ewing sarcomas can also occur in the head and neck region.
The most frequent mode of presentation of a bone tumor is a mass lesion or symptoms that result from pressure on contiguous neurovascular structures or viscera or the adjacent dentition. However, many small lesions are discovered incidentally on imaging studies performed for other reasons. Symptoms also may arise for tumors of the maxilla as a result of compression of the orbit, or displacement of the orbital contents, or obstruction of the nasal passages. Thorough radiographic evaluation and tissue diagnosis, is mandatory for surgical treatment planning.
Accurate assessment of the anatomic extent of a lesion of the craniofacial skeleton requires its evaluation in all three dimensions. Plain films of the mandible and skull are used rarely. A panoramic radiograph (orthopantomogram) of the mandible provides an overview of the dentition and architecture of the mandible ( Fig. 16.9 ). However, for more detailed assessment of the mandible, a computed tomography (CT) or magnetic resonance imaging (MRI) scan is required. A CT scan is excellent for bony architecture, whereas assessment of the soft tissues and bone marrow and inferior alveolar nerve in the mandible is better with MRI. Whenever a CT scan is requested for evaluation of a neoplastic process with invasion of bone and soft tissue, the scan should be obtained with contrast enhancement, and both soft tissue and bone windows should be carefully scrutinized.
The patient whose CT scans of the upper alveolus are shown in Figs. 16.10 and 16.11 has a myxoma of the alveolus extending into the maxilla. The soft-tissue window shown in Fig. 16.10 gives excellent soft-tissue detail, but the fine architectural detail of the bone is obscured. On the bone window shown in Fig. 16.11 , the soft-tissue detail is obscured and the fine architecture of the bone and the lesion are clearly seen. Thus for adequate evaluation of bone invasion by a neoplastic process, both soft tissue and bone windows of the CT scan are required. An axial view of the CT scan of a patient with a massive expansile cystic lesion involving the body of the mandible on the left-hand side with significant expansion of the lateral cortex of the mandible is shown in Fig. 16.12 . The lesion has a uniform ground glass appearance without any bone destruction or new bone formation. The reconstructed sagittal view of the CT scan shown in Fig. 16.13 demonstrates a large, unilocular cystic space extending from the region of the retromolar trigone posteriorly up to the lateral incisor anteriorly. The cystic space has clear content and a smooth margin that is well defined. The roots of the teeth are within the cystic space. Three-dimensional reconstruction of the CT scan images clearly demonstrate the large expansile cystic lesion with bone loss in the body of the mandible ( Fig. 16.14 ).
Three-dimensional reconstruction of CT images are very helpful in surgical treatment planning for resection and reconstruction. Three-dimensional computer-aided design/computer-aided manufacturing (CAD-CAM) models can also be fabricated with computer software, which provides three-dimensional printed guides for bone resection and reconstruction, thus facilitating the ability of the reconstructive surgeon to accurately fabricate a graft or flap to achieve exact contour and symmetry (see Chapters 17 and 18 ). A three-dimensional reconstruction of the mandible of a young patient with fibrous dysplasia of the mandible is shown in Fig. 16.15 . Note the shape and dimensions of the lesion of the mandible in relation to the remaining facial skeleton. In a posterior view of the reconstructed CT scan, the thickness of the mandible involved by fibrous dysplasia is vividly demonstrated ( Fig. 16.16 ). An axial view of the CT scan of the same patient shows thickening of the cancellous bone with thinning out of the mandibular cortex. The normal architecture of the cancellous bone is lost and is replaced by a ground glass appearance due to fibrous dysplasia ( Fig. 16.17 ).
Paget’s disease of the craniofacial skeleton has a characteristic appearance on a CT scan with thickened bones with an irregular ground glass patchy appearance. Malignant transformation in a bone involved with Paget’s disease clearly shows a punched-out demarcation with the sarcoma in the involved bone, while the remaining bone shows the Paget’s disease in the background ( Fig. 16.18 ). The radiographic appearances of several other bone lesions are shown later in this chapter as the surgical procedures are described. Many tumors and tumorlike conditions have characteristic radiographic appearances that almost pinpoint the diagnosis. However, tissue diagnosis is mandatory before implementation of therapy.
It is vitally important that accurate tissue diagnosis be established before definitive surgical treatment in patients who present with lesions suspicious of being a neoplastic process involving the facial skeleton. Several bone lesions are benign or of a low-grade malignant histology, and their treatment is significantly different than for high-grade malignant tumors. Because needle biopsy is often not satisfactory, an open biopsy with a generous volume of representative tissue should be submitted for pathologic analysis. Frozen section diagnosis is generally not possible and should not be requested when a bone tumor is suspected. Extraction of a tooth near lesions of the upper or lower jaw should be avoided, and a biopsy from an adjacent area should be obtained to prevent implantation of malignant tumor into the marrow cavity of the affected bone, which would increase the risk of tumor dissemination.
The World Health Organization (WHO) histologic classification of bone tumors is shown in Table 16.1 .
|TISSUE OF ORIGIN||BENIGN||MALIGNANT|
|Fibrohistiocytic||Fibrous histiocytoma||Malignant fibrous histiocytoma|
|Primitive neuroectodermal||Ewing sarcoma|
|Hematopoietic||Plasma cell myeloma|
|Giant cell||Giant cell tumor||Malignant giant cell tumor|
|Miscellaneous tumors||Adamantinoma||Metastatic malignancy|
|Miscellaneous lesions||Aneurysmal bone cyst|
|Osteo fibrous dysplasia|
|Langerhans cell histocytosis|
|Chest wall hamartoma|
|Joint lesions||Synovial chondromatosis|
Soft-tissue chondromas (synonyms: fibrochondroma, myxochondroma, osteochondroma, chondroma of soft parts, extraskeletal chondroma) are benign cartilaginous tumors that, on rare occasion, may arise in the larynx and craniofacial bones, including the palate. These benign tumors may also occur extraskeletally, whereby they are referred to as soft-tissue chondromas. They present as well-circumscribed, nodular masses and may be particularly difficult to differentiate histologically from low-grade chondrosarcoma, particularly on small biopsy samples. These tumors are composed of mature hyaline cartilage with a lobular pattern of growth and cells that are immunoreactive for S-100 protein. Although they do not generally dedifferentiate to chondrosarcoma, incomplete excision of these tumors may lead to local recurrence.
Chondrosarcoma is the malignant counterpart to chondroma and is defined as a malignant tumor of hyaline cartilage. Like chondromas, these are rare neoplasms of the head and neck, but when they occur, they most commonly arise in the maxilla, mandible, larynx, and nasopharynx, in decreasing order of frequency. These tumors are composed of nodules of myxoid and hyaline cartilage, with neoplastic chondrocytes displaying varying degrees of atypia ( Fig. 16.19 ). The severity of atypia defines tumor grade in a three-tiered grading system. Increasing grade is characterized by increasing pleomorphism, mitotic activity, abnormal mitotic figures, and binucleation. Differentiating grade III chondrosarcoma from chondroblastic osteosarcoma is of prognostic significance, because the former has a much better outcome. Ancillary studies are not generally necessary for diagnosis; rather, the absence of osteoid allows distinction of high-grade chondrosarcoma from the chondroblastic osteosarcoma. Metastases are infrequent, with an 83% 5-year survival for grade I chondrosarcoma and 53% combined 5-year survival for grades II and III.
Osteoid osteoma (synonym: osteoma) is a slowly growing, hamartomatous or developmental lesion composed of cortical bone. It has no malignant potential and may indeed regress in size over time. There is some association between multiple osteomas and Gardner’s syndrome. Osteomas most commonly arise from the metaphyses of long bones. In the head and neck, they generally involve the frontal bone, calvarium, mandible, or sinonasal bones. They present as small lesions, 1 to 2 cm in size, with a central nidus of proliferating cells that appear less dense than the adjacent bone on radiographic imaging. Histologically, these are bland proliferations of dense bony spicules, morphologically similar to the surrounding bone, rimmed by osteoblasts, and surrounded by fibrous tissue with an abundance of vessels ( Fig. 16.20 ). Sclerotic bone may surround the lesion.
Osteosarcoma (synonyms: osteogenic sarcoma, osteoblastic sarcoma, chondroblastic osteosarcoma, medullary osteosarcoma) is a malignant tumor defined by neoplastic bone formation. The WHO classification includes several morphologic variants (e.g., chondroblastic, fibroblastic, telangiectatic, small cell), as well as variants based on the site from which the tumor arises (e.g., periosteal versus endosteal). Grossly, these are hard, destructive osseous neoplasms, which, in the head and neck, are most commonly intraosseous in location. The mandible is the most common primary site, followed by the maxilla and the skull. Histologically, these are matrix-producing tumors whose neoplastic osteoblasts produce bone. These malignant osteoblasts are usually highly pleomorphic and may be plasmacytoid, spindled, epithelioid, or round or have a mixture of these features ( Fig. 16.21 ). Approximately half of all lesions are high grade. Ancillary studies are generally not used in the pathologic diagnosis of osteosarcoma. If a patient has been treated with preoperative chemotherapy, histologic grading of therapeutic response should be reported because it is an important predictor of outcome.
Plasmacytoma (synonyms: plasma cell myeloma, solitary plasmacytoma of bone, myeloma) is a malignant primary neoplasm of bone composed of plasma cells. When present as a single, localized mass, defined by a proliferation of clonal, terminally differentiated B cells (plasma cells), the lesion is a called a plasmacytoma. When there are multifocal, lytic bone lesions, this malignant proliferation of plasma cells is termed multiple myeloma. Histologically, these tumors are made up of a uniform population of lymphoid cells with eccentric nuclei, which are round to oval, demonstrating a pattern of chromatin distribution referred to as “clock face chromatin.” When there is marked nuclear pleomorphism, with increased and abnormal mitoses, the tumors may be referred to as “undifferentiated” or “anaplastic” or “poorly differentiated.” The malignant plasma cells demonstrate immunoreactivity to antibodies against CD138, CD79a, and vimentin, whereas LCA (leukocyte common antigen) and CD20, which are both normally expressed by mature B cells, are negative. These tumors can also occur in soft tissue, as shown in this patient with a laryngeal plasmacytoma ( Fig. 16.22 ). Plasmacytomas often also demonstrate light chain restriction, either kappa or lambda. Prognosis depends on stage, with systemic disease defined by high mortality rates at 3 years and an approximately 10% 10-year survival.
Giant cell granuloma (synonyms: giant cell reparative granuloma, solid aneurysmal bone cyst, brown tumor, central giant cell lesion) is an osteolytic, poorly defined intraosseous lesion of the jaw defined by an abundance of osteoclast-type giant cells that can be seen irregularly distributed throughout a background of proliferating reactive blood vessels and fibroblasts and often with associated hemorrhage. In the past, these lesions were deemed purely reactive, but there appears to be some recent molecular evidence that they may be related to aneurysmal bone cysts, with associated identical translocations. The exact same histologic appearance may also be seen in hyperparathyroidism, and the lesion is then called a brown tumor, although the molecular aberrations are distinct from giant cell granuloma. Microscopically, it is unencapsulated and has nests of multinucleated osteoclast-type giant cells in a fibrovascular stroma ( Fig. 16.23 ). Ancillary studies are not necessary in the diagnosis, although it is important to evaluate serum calcium levels and parathyroid hormone to exclude hyperparathyroidism. It is also important to differentiate this lesion from giant cell tumor of bone, as behavior, prognosis, and treatment can be different.
Giant cell tumor of bone is a benign, but potentially aggressive neoplasm, which on rare instances may be seen in the craniofacial bones. On radiographic imaging, it has poorly defined borders and presents as a destructive, lytic lesion. Histologically, giant cell tumors share many morphologic features with giant cell granuloma; however, there is also a proportionate abundance of mononuclear cells and the giant cells are often very large, with 50 to 100 nuclei. Although mitotic activity is common, abnormal mitoses are not seen. These tumors can recur, can be very locally destructive, and do metastasize infrequently.
Ewing sarcoma and primitive neuroectodermal tumor (synonyms: primitive neuroepithelioma; ES/PNET, EWS) is a malignant “small round blue cell tumor” of bone and soft tissue, composed of undifferentiated cells of neuroectodermal origin. Almost 10% of Ewing sarcomas arise in the head and neck, most commonly in the mandible, followed by the maxilla. It may have a bimodal age distribution, with a higher frequency peak in children, and then a second, much smaller peak in older adults. On rare occasions, Ewing sarcoma may be metastatic to the jaw. Histologically, these tumors are high grade by definition and are composed of primitive, small, round uniform cells, which may form rosettes and fibrillary processes ( Fig. 16.24 ). Tumors in the ES/PNET group are characterized by a EWS-FLI fusion, t(11;22) (q24;q12), with several variants of this translocation producing other fusion products. The particular translocation and the corresponding fusion transcript directly affect the outcome, and long-term survival may be as high as 85%.
Undifferentiated pleomorphic sarcoma (UPS) (synonyms: malignant fibrous histiocytoma, MFH, xanthosarcoma, malignant fibrous xanthoma, fibroxanthosarcoma, malignant histiocytoma) is a high-grade malignant neoplasm of soft tissue or bone and is essentially a diagnosis of exclusion. It is a malignant storiform neoplasm arising from histiocytes ( Fig. 16.25 ) or from cells capable of histiocytic differentiation. Because this tumor’s immunophenotype is nonspecific and the diagnosis is made by excluding other neoplasms, immunohistochemistry is used to rule out other spindle cell neoplasms of definable lineage.
Extrapleural solitary fibrous tumor (SFT; synonyms solitary fibrous tumor; hemangiopericytoma (obsolete); giant cell angiofibroma) is categorized by the WHO (2017) as a mesenchymal neoplasm of fibroblastic type that forms staghorn-patterned or “hemangiopericytoma-like vascular patterns, which are most commonly benign, although there is a malignant SFT as well. The tumor cells are positive for CD34, bcl2, and CD99; 20% to 30% show variable immunoreactivity for EMA and SMA. More than 70% of these tumors are benign, and histology is not necessarily predictive of behavior, although those with marked mitotic activity, necrosis, and nuclear pleomorphism are more likely to metastasize.
The WHO (2017) classification of odontogenic tumors divides these pathologic entities into malignant odontogenic tumors (carcinomas and sarcomas), benign odontogenic tumors (epithelial, mesenchymal, and mixed origin), and odontogenic cysts (developmental or inflammatory) ( Table 16.2 ).
|TISSUE OF ORIGIN||BENIGN||MALIGNANT|
Ameloblastoma is a benign tumor of ameloblasts, which essentially recapitulates the development of the early tooth-forming apparatus without the formation of enamel or its precursors. As a group, 20% are seen in the maxilla, and 80% occur in the mandible, distributed as follows: 70% molar and ascending ramus, 20% premolar region, and 10% incisor region. They are divided into unicystic ameloblastoma, multicystic or solid ameloblastoma, peripheral ameloblastoma, and malignant ameloblastoma. The pathologic classification further defines ameloblastoma into four varieties: (1) conventional, (2) unicystic, (3) extraosseous/peripheral, and (4) malignant (metastasizing) ameloblastoma. Histologically, these tumors contain nests and islands of odontogenic epithelium with central stellate reticulum-like cells surrounded by peripheral tumor cells that most commonly have subnuclear vacuoles ( Fig. 16.26 ). Unicystic ameloblastoma is unilocular and cystic with an epithelial lining consisting of ameloblastoma cells. This entity is seen to arise in young adults, almost exclusively in the mandible, with more than two-thirds of the lesions in the molar-ramus region. These are thought to be less aggressive than multicystic ameloblastoma. Unfavorable prognostic indicators for ameloblastoma include maxillary location in an older adult and extension of tumor from bone into adjacent soft tissue. Marked mitotic activity, nuclear pleomorphism, tumor necrosis, and evidence of metastasis would indicate a diagnosis of malignant ameloblastoma.
OKCs are cystic lesions that may be associated with the roots of teeth or impacted teeth and represent 5% to 15% of all odontogenic cysts. In up to almost 80% of cases of Gorlin-Goltz syndrome (also known as nevoid basal cell carcinoma syndrome ), the diagnosis of OKC may be the first diagnostic indicator of the underlying genetic disorder. Histologically, these lesions typically display a stratified squamous epithelium of six to eight layers with a corrugated parakeratinized surface layer ( Fig. 16.27 ). These lesions may be locally aggressive, with recurrence rates reported around 30%. Local recurrence has been correlated with the presence of islands of odontogenic epithelium in the cyst wall. There are rare case reports of squamous cell carcinoma arising in these lesions, but that is the exception and not the norm.
Principles and Goals of Treatment
Surgical excision is the preferred modality of therapy for nearly all bone tumors arising in the head and neck region. Most symptomatic benign lesions can be treated adequately by a relatively conservative excision but preferably in a monobloc fashion depending on the size and location of the tumor. In a similar fashion, low-grade malignant tumors such as a low-grade chondrosarcoma and low-grade fibroosseous lesions also are managed by a relatively conservative surgical resection. On the other hand, high-grade malignant tumors require an aggressive surgical approach for satisfactory resection with adequate bone and soft-tissue margins. Histologically aggressive tumors require multimodality treatment to improve local control and reduce the risk of local recurrence or distant metastases. Solitary, symptomatic metastatic tumors to the craniofacial skeleton from primary carcinomas of the kidney, thyroid, lung, and breast occasionally may require surgical resection. Some lesions such as fibrous dysplasia are polyostotic. Involvement of multiple bones clearly would influence the decision for surgical treatment. Appropriate workup therefore should be undertaken to rule out multiple bone involvement.
Lesions of odontogenic origin usually are managed in a conservative fashion. An ameloblastoma is a locally invasive process that usually is treated by “complete excision” to avoid local recurrence. Small, localized ameloblastomas may be suitable for a relatively conservative excision, but larger tumors require complete resection that may include a segmental mandibulectomy or a maxillectomy. Similarly, small cystic ameloblastomas can be treated by curettage and marsupialization, but larger lesions require more aggressive resection. Curettage for larger lesions is unlikely to be successful and almost uniformly results in recurrent disease.
Neoadjuvant multidrug chemotherapy followed by surgical resection has become the standard of care for treatment of osteosarcoma of the extremities in the pediatric age group. The efficacy of this approach in head and neck osteosarcomas in the adult is however unproven. Thus primary surgical resection followed by adjuvant radiation therapy currently is recommended as the most effective treatment for head and neck osteosarcomas. Chondrosarcomas and other rare variants of bone sarcomas generally are treated with appropriate surgical resection. Proton beam radiation therapy for chondrosarcomas in an adjuvant setting has shown improved local control compared with conventional radiation therapy with photons. Treatment options for Ewing sarcoma have improved with the use of multidrug chemotherapy and radiation therapy, reserving salvage surgery for residual disease. A plasma cell tumor generally is managed with radiation therapy, keeping surgery in reserve for salvage. Treatment for multiple myeloma and lymphoma is systemic chemotherapy with or without radiation therapy.
Most patients requiring surgery for tumors of the craniofacial bones do not need any specific preoperative preparation other than imaging studies and accurate tissue diagnosis. If a massive resection is contemplated where significant blood loss is anticipated, then sufficient quantities of blood should be available to replace operative blood loss. Highly vascular lesions may be considered for preoperative embolization before surgical resection.
If the upper alveolus or maxilla is to be resected, then preoperative consultation from the maxillofacial prosthetic department should be obtained for preoperative dental impressions and fabrication of a dental obturator. If surgical resection entails orbital exenteration or resection of a major portion of facial bones, then preoperative photographs and facial moulage should be obtained for fabrication of facial/orbital prostheses. On the other hand, if bone reconstruction is planned after resection of the tumor, then CAD-CAM planning and modeling is strongly recommended to reduce operating time in designing an appropriate free bone flap to achieve accurate reconstruction. (See Chapter 17 for details.) Similarly, if a mandibulectomy is planned, then a microvascular free flap reconstruction from an appropriate donor site, generally from the fibula, should be planned with assistance of CAD-CAM modeling.
Lesions involving the calvarium or the skull base require neurosurgical consultation for a combined craniofacial approach for adequate surgical resection. In patients requiring craniofacial resections, antibiotics and steroids should be administered preoperatively to reduce the risk of postoperative sepsis and brain edema. Surgical resection of vertebral bodies requires adequate stabilization of the spine, which may require either neurosurgical or orthopedic consultation for posterior stabilization of the spine or to ascertain the availability of a halo splint for postoperative immobilization.
The operative procedures in this chapter are not discussed by tissue of origin, as was done in the chapter on soft-tissue tumors. Instead, the management of osseous tumors is described by the bones of origin, starting from the calvarium, skull base, maxilla, mandible, and cervical spine.
Tumors of the Calvarium
Primary bone tumors of the calvarium are exceedingly rare. The benign lesions most frequently seen are osteomas and hemangiomas. The malignant tumors most frequently seen are osteogenic sarcoma, chondrosarcomas, other sarcomas, and metastatic lesions. The indications for surgery are related to histologic diagnosis and symptoms. Some benign lesions are asymptomatic and may simply be kept under observation.
Hemangioma of the Frontal Bone
Hemangiomas of the craniofacial skeleton are usually asymptomatic and present simply as a bony mass. On occasion the lesions get large and produce a skeletal deformity that requires surgical intervention. In addition, because of the progressive growth of the lesion, some patients have symptoms that warrant surgical intervention. A hemangioma in a stress-bearing bone may require surgical intervention to avoid a pathologic fracture. The most common site of hemangiomas in the craniofacial skeleton is the calvarium. The CT scan of a patient with a hemangioma of the parietal region is shown in an axial view ( Fig. 16.28 ). Note the well-demarcated bony defect and the honeycomb appearance of the involved outer cortex of the calvarium. The bone window of the CT scan demonstrates a punched-out area of the frontoparietal region involved by the hemangioma ( Fig. 16.29 ). The lesion had shown growth over the course of a year and was symptomatic with local pain at the site.
Surgical excision of the lesion requires a full-thickness craniectomy and an appropriate cranioplasty. The entire operative procedure is extradural. The patient is placed under general endotracheal anesthesia, and the scalp is shaved and prepared in the usual fashion. A U-shaped incision is made over the scalp around the palpable tumor, with the pedicle of the flap based anteriorly. The scalp flap is elevated deep to the pericranium, exposing the outer cortex of the frontoparietal region ( Fig. 16.30 ). Note the purplish color of the hemangioma involving the bone. Two burr holes are made, one anterior and the other posterior to the lesion. With use of appropriate dural elevators, the underlying dura is separated from the inner cortex of the bone to free the area of bone involvement. A Midas Rex side-cutting power saw is used to complete the craniectomy by connecting the burr holes around the visible and palpable tumor. The surgical specimen is removed in a monobloc fashion ( Fig. 16.31 ). Accurate hemostasis is secured by using bipolar cautery for control of bleeding from the dura and bone wax over the cut edges of the calvarium.
A cranioplasty of the craniectomy defect can be performed with a variety of different techniques. The simplest technique is to use a braided wire and bone cement. The wire is crisscrossed between the edges of the surgical defect, and bone cement is used to fill the surgical defect. The wire acts as a matrix over which the bone cement is spread to provide a shell to repair the craniectomy defect ( Figs. 16.32 and 16.33 ). Alternatively, a titanium mesh can be used to provide a matrix of support for the bone cement, or special cranioplasty plates may be used without the bone cement to repair small surgical defects ( Fig. 16.34 ). On the other hand, a computer-assisted cranioplasty prosthesis can be fabricated from Porex. The scalp incision is then closed over the cranioplasty in the usual manner.
Sarcoma of the Frontal Bone
Malignant tumors of the calvarium that are adherent to the overlying scalp and underlying dura require through-and-through monobloc resection. However, when these tumors involve the anterior cranial fossa, a craniofacial resection becomes necessary. If the tumor involves one orbit, then orbital exenteration in conjunction with a formal craniectomy and en bloc excision is indicated.
The patient described here has Paget disease involving the skull. He presented to a local surgeon with an enlarging mass on his forehead of approximately 6 months’ duration. A generous open biopsy was performed with a transverse incision in the skin of the forehead, which confirmed the diagnosis of osteogenic sarcoma ( Fig. 16.35 ).
A CT scan of the head in an axial plane with a soft-tissue window shows significant intracranial extension of disease with displacement and/or involvement of the dura and the frontal lobe on the left-hand side ( Fig. 16.36 ). A representative axial view of the CT scan with a bone window shows the entire skull involved with Paget’s disease ( Fig. 16.37 ). The tumor involves the frontal bone on the left-hand side with extension of disease to involve the medial part of the frontal bone on the right-hand side. Significant soft-tissue extension is present in an extracranial fashion. A coronal view of the CT scan shows direct extension of the tumor in the orbit through its roof, displacing the globe inferiorly and laterally ( Fig. 16.38 ). However, the tumor does not extend to involve the contents of the nasal cavity.
The operative procedure in this clinical setting requires involvement of two surgical teams. A neurosurgical team will begin with the craniotomy, and the head and neck team will accomplish the facial aspect of the procedure and reconstruction of the surgical defect with appropriate scalp flaps. A third surgical team for microvascular free tissue transfer may be required if free flap reconstruction of the surgical defect is planned. The technical details of craniofacial resection are discussed in Chapter 6 . An artist’s rendering of the extent of the tumor resection is shown in Fig. 16.39 .
The surgical specimen shows the orbit, the frontal bone with the tumor, and the overlying skin excised in a monobloc fashion ( Fig. 16.40 ). The posterior view of the specimen shows the excised portion of the dura and the frontal lobe ( Fig. 16.41 ). The surgical defect of the craniectomy is continuous with the lower half of the orbital socket and the contents of the frontal fossa with exposed brain in that region. A close-up view of the surgical defect shows exposed brain of the left frontal lobe with a large dural defect due to its resection with the specimen ( Fig. 16.42 ). Laterally, the stump of the temporalis muscle is visible in the temporal region.
A large segment of the periosteum from the posterior aspect of the skull is now excised and used as a free graft to repair the defect in the dura. The periosteum is sutured to the dura with 4-0 Nurolon sutures. A watertight closure is obtained to prevent any cerebrospinal fluid (CSF) leakage ( Fig. 16.43 ).
A massive defect such as this is best reconstructed with a computer-assisted Porex prosthesis for bone reconstruction and soft tissue and skin free flap for coverage. A postoperative CT scan demonstrates total excision of the tumor of the frontal region with satisfactory margins ( Fig. 16.44 ).
Metastatic Tumor to the Calvarium
Tumors of the calvarium that involve the overlying scalp require a through-and-through resection, often including the underlying dura. Primary tumors of the scalp invading the skull and primary tumors or symptomatic metastatic tumors of the calvarium warrant this type of surgical resection.
The plain radiographs of the skull demonstrate a bone-destructive lesion involving the cranial vault in the parietooccipital region on the right-hand side ( Figs. 16.45 and 16.46 ). The soft-tissue windows of the CT scan of the patient shown here clearly demonstrate a bone-destructive lesion, which involves the overlying scalp with extension through the cranium to involve the underlying dura ( Fig. 16.47 ). The extent of bone destruction is shown by a punched-out area of the calvarium on the bone window ( Fig. 16.48 ). A needle aspiration biopsy of this lesion confirmed the diagnosis of metastatic renal cell carcinoma that was a solitary metastasis.
The patient is placed under general anesthesia in the supine position on the operating table with the left parietal region of the head resting on a standard U-shaped head rest ( Fig. 16.49 ). The shaved scalp clearly shows the gross dimensions of the lesion. An indwelling spinal catheter is placed to monitor CSF pressure and to facilitate withdrawal of CSF to slacken the brain if necessary.
The incisions are outlined on the scalp ( Fig. 16.50 ). The extent of the scalp that will need to be sacrificed to resect the tumor is shown. A parietal scalp flap is outlined; this scalp flap is based on the left-hand side, with the entire scalp elevated from the pinna of the ear on the right-hand side all the way up to the pinna of the ear on the left-hand side ( Fig. 16.51 ). The blood supply to this flap is derived from the superficial temporal, posterior auricular, and occipital arteries of the left-hand side. The scalp flap is elevated all the way up to the pinna of the ear and the mastoid process on the left-hand side. The flap is elevated in a subgaleal plane, remaining superficial to the pericranium, which will be used later to repair the defect.