Sinonasal Neoplasms
Evaluation and staging of sinus neoplasms is achieved through a combination of clinical assessment and pretreatment imaging with close scrutiny of the sinonasal cavity, orbits, nasopharynx, oral cavity, cranial nerves, and the intracranial compartment. Imaging is especially important in assessing the skull base and the intracranial compartment, and in distinguishing the tumor from coexistent inflammatory changes. CT and MRI play complementary roles in evaluating sinonasal neoplasms.2,7,16,24–26,64–73 Both are usually obtained in the evaluation of patients with sinonasal masses. CT is more sensitive and accurate in assessing the osseous margins of the sinonasal cavity, the osseous floor of the anterior cranial fossa, as well as the walls of the orbit.7,15,18,25,69,74–76 MRI offers improved soft tissue resolution, contrast, and multiplanar capabilities allowing better evaluation of disease extension outside the sinonasal cavity. An extension of the neoplasm outside of the sinonasal cavity into the adjacent anatomic locations significantly impacts upon the patient′s operability, the type of resection that will occur, the surgical approach, the necessity for radiation therapy, the placement of radiation portals, and the prognosis.
Benign neoplasms, when large enough, expand the paranasal sinus that they affect and secondarily remodel the adjacent bone. Osseous destruction from benign lesions is less common than with malignancies. However, it is not unusual for contained malignant tumors to have benign imaging features and, conversely, benign tumors to have an aggressive appearance. Papillomas arise from the columnar epithelium and include inverted, cylindric, and fungiform subtypes. Typically, papillomas occur uni-laterally in the sinonasal cavity.77,78 Inverted papillomas are most common and are benign; however, squamous cell carcinoma may be present in 5 to 15% of cases.77,78 Papillomas typically arise from the lateral nasal wall at the level of the middle turbinate or, less commonly, within the maxillary sinus. Although a convoluted cerebriform pattern is thought to be associated with an inverted papilloma, it may be seen with other malignancies.79 Location is usually a tip-off to the diagnosis.80,81 A focal ostetis on CT imaging may indicate the site of attachment of an inverted papilloma. Inverted papillomas may show a rather aggressive appearance with bony destruction, and occasionally they may erode the skull base (as may benign polyps), simulating a malignant tumor.82
Unilateral opacification of the olfactory strut in the absence of other findings in the paranasal sinuses usually represents a CSF leak, a meningoencephalocele, or a neoplasm such as an esthesioneuroblastoma ( Fig. 3.13A–C ). Caution is always required when evaluating masses within the paranasal sinuses. Fibroosseous lesions such as osteomas, fibrous dysplasia, ossifying or nonossifying fibromas, and chondroid lesions may mimic a malignant mass on MRI. However, these lesions usually have characteristic radiologic appearances on CT imaging ( Figs. 3.14A,B and 3.15A–C ).
Malignant Neoplasms
Carcinomas of the sinonasal cavity constitute 3 to 4% of all head and neck neoplasms.2,65,83,84 In general, they have a relatively poor prognosis because many present at advanced stages. Squamous cell cancer accounts for ~80% of sinonasal carcinomas. Approximately 25 to 60% of squamous carcinomas involve the maxillary antrum; however, the maxillary sinus is secondarily involved by direct extension in 80% of patients. Approximately 30% of squamous carcinomas arise in the nasal cavity, and 10% in the ethmoid air cells. Occupation exposures include nickel, chromium pigment, Bantu snuff, Thorotrast, mustard gas, polycyclic hydrocarbons, cigarettes, and isopropyl alcohol.2,85 Approximately 10% of sinonasal tumors arise from minor salivary glands.2,65,83,86 There is a spectrum of histologic types, including adenoid cystic, mucoepidermoid, undifferentiated, and adenocarcinoma. Adenoid cystic carcinomas are most common, accounting for one-third of minor salivary gland neoplasms.87 Adenocarcinomas may represent minor salivary gland tumors or intestinal-type adenocarcinomas, and have a predilection for the ethmoid air cells.88–90 These may be more common in wood and leather workers.38 They are frequently advanced at presentation, with cribriform plate erosion present in up to 50% of cases. Dural invasion is not uncommon.90
Delayed presentation is typical of sinonasal malignancies as there is a relative paucity of pain associated with these neoplasms. Because there is frequently coexistent inflammatory disease in the paranasal sinuses that may elicit mild pain, a tumor may initially be overlooked as the patient is treated for presumed infection. Although pain in the early stages of sinonasal malignancies is uncommon, the presence of pain is usually an indication of advanced disease. Pain may indicate perineural tumor spread, skull base extension, or spread to the infratemporal fossa. Other clinical presentations include nasal congestion and epistaxis.
The treatment of choice for sinonasal carcinomas usually includes combined surgery and irradiation.91–96 Orbital exenteration is often necessary when a tumor involves the orbital contents, usually confirmed during intraoperative assessment.97,98 In the setting of extension into the central skull base, curative surgery is usually not attempted. The main cause of treatment failure is local recurrence.83,99
Findings on CT scans that should raise one′s index of suspicion for something other than inflammatory disease include unilateral nasal mass/tissue, unilateral opacification of the olfactory strut, bone destruction, and extension of disease outside the sinonasal cavity. In these cases, MRI often provides important additional information and should be obtained. In suspected sinonasal malignancies, CT and MRI should be completed when possible prior to surgical intervention, including biopsy.64,100 Advances in pretherapeutic imaging have contributed significantly to the management of sinonasal tumors. Imaging may provide important information regarding the origin of the neoplasm, the extent of the neoplasm, as well as the presence of tumor vascularity. Preoperative imaging may allow optimal localization for tissue biopsy, and may be extremely useful in preparing the surgical approach and minimizing complications.
MRI plays a critical role in distinguishing sinus opacification related to a tumor from that related to inspis-sated secretions.7,14,15 Most neoplasms have a more solid enhancement pattern101,102 following intravenous contrast administration, compared with peripheral enhancement seen in benign inflammatory conditions. However, benign masses, such as polyps, may also demonstrate peripheral enhancement. In addition, T2-weighted imaging may be helpful as most histologic types of sinonasal tumors are highly cellular, resulting in intermediate-to-low signal intensity of these tumors on T2-weighted images (similar to the brainstem) compared with inflammatory secretions that tend to be hyperintense (bright).
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