Evaluation/Diagnosis

As seen already in other chapters, when presented with an orbital mass the treating clinician must first decide whether the mass is an infectious or inflammatory condition, or whether it represents a true neoplasm. This determination can generally be made with an astute elicitation of history from patients, caregivers, or parents, thorough examination (vital signs, a complete head and neck examination, visual acuity, and ophthalmologic examinations), and laboratory testing(white blood cell count, red cell count, and sedimentation rate) and imaging. Several imaging modalities may have complementary roles and these may include ultrasound, computerized tomography (CT scan) and magnetic resonance imaging (MRI) (see Chapter ▶ 4). These tests enable the clinician to differentiate the infectious or inflammatory conditions from true neoplasms. If an intraconal neoplasm is suspected, the next step is to make a histopathologic diagnosis. When possible, fine needle aspiration can be very helpful and minimizes the risk of seeding tumor. Fine needle aspiration is particularly useful for tumors in the lateral orbit involving the lacrimal gland, as well as tumors generally located in the anterior orbit. Tumors more posterior in the orbit or those that may involve the optic nerve might be best suited by a direct surgical biopsy. The clinician is encouraged to develop a careful differential diagnosis so that any incision on the face or on the eyelids is made with consideration of the need for subsequent surgical management. Possible approaches besides fine needle aspiration can include transconjunctival, subciliary, brow, direct access through the oral cavity and the buccal gingival sulcus, or—as in the case of many medially placed and posteriorly placed lesions—transnasal endoscopic approaches. The latter approaches are particularly appealing when the lamina papyracea or intrasinus contents will be a component of the overall definitive surgical approach. However, several tumors may be located in areas where a biopsy may pose a serious risk of loss of vision. In such cases, radiological imaging can be very useful in narrowing down the diagnosis.

Often, several tumors such as orbital hemangioma have classic pathognomic features ( ▶ Fig. 13.1) and a biopsy may be bypassed in favor of close and watchful observation with repeat imaging. In addition, a nonneoplastic mass such as orbital dermoid also has a classic appearance ( ▶ Fig. 13.2) that can be observed without biopsy. Orbital involvement by lymphoma is not unusual in patients with systemic leukemia-lymphoma and often these may not require additional biopsy in known disease history. Bony tumors such as ossifying fibroma ( ▶ Fig. 13.3) and osteoma have a classic appearance on CT. In several infiltrative lesions close to the orbital apex, the optic nerve, and the optic canal, the history may be suspicious for orbital pseudo tumor, and response to a trial of systemic glucocorticosteroids can often be diagnostic as well as therapeutic. IgG₄-related disease is another newly described inflammatory entity mediated by plasma cells that can afflict the orbit, lacrimal gland, and paranasal sinuses and present as a mass. Biopsy can be avoided if other afflicted areas are available for safer sampling, and these lesions also tend to respond to immunosuppressant and corticosteroid therapy.

Orbital tumors are generally evaluated radiographically by CT scanning, either with or without contrast (or preferably both). Images should be available and studied in all three planes (coronal, sagittal, and axial planes) to map the tumor and obtain a three-dimensional understanding of the lesion and surrounding pertinent anatomy The MRI scan is critical in refining the diagnosis and assessing soft tissue invasion of tumors, and must be performed for almost all complex orbital pathology for diagnostic or management purposes ( ▶ Fig. 13.4) (see ▶ 4). In the case of carcinomas, particularly the high-grade ones, as well as sarcomas and other mesenchymal tumors, body-wide staging with total body PET/CT scanning may be important.

In general, patients with intraconal orbital tumors should be evaluated from the beginning by a multidisciplinary team of experts including ophthalmologists specializing in orbital surgery, otolaryngologists with special training in head and neck surgery, and specialists in endoscopic skull base surgery, medical oncology, radiation oncology, pathology, and neuroradiology.

13.4 Classification of Tumors

Classification of orbital and orbit-related tumors is complicated. In general, orbital lesions can be grouped into inflammatory, primary, and secondary or metastatic. Several authors subclassify true neoplasms (either primary or secondary) into intracoronal or extracoronal on the basis of the anatomical location. The reader is referred to ▶ Table 13.1, ▶ Table 13.2, and ▶ Table 13.3 for lists of common inflammatory conditions ( ▶ Table 13.1), benign primary tumors ( ▶ Table 13.2), and primary and secondary malignant tumors ( ▶ Table 13.3) that involve the orbit. These tables are not comprehensive, as several rarer tumors can affect the orbit, but they provide a reference framework for the treating physician to begin with.

13.5 Orbital Neoplasia

13.5.1 Benign Lesions

While this chapter will focus primarily on malignant neoplasms of the orbit, occasionally the clinician is faced with a benign lesion. Lacrimal gland tumors are quite uncommon, representing as few as 2% of all the neoplasms identified in the orbit. ^{2,​ 3} Approximately half of the lacrimal gland masses represent inflammatory lesions, cystic lesions, or lymphatic lesions, and are generally benign. Approximately half of lacrimal gland masses or tumors are true neoplasms and are split generally evenly between benign mixed tumors (pleomorphic adenoma) or carcinomas, with adenoid cystic being most common and mucoepidermoid carcinomas being less common. Carcinoma ex pleomorphic adenoma is more common in the lacrimal gland than it is in other salivary type glands. Pleomorphic adenomas in this gland can be resected through a lateral orbital approach; however, in the experience of the authors, even benign tumors of the lacrimal gland tend to be more fibrotic and more difficult to operate on than their counterparts in traditional salivary gland tissue.

Lymphatic malformations and true hemangiomas (which are true neoplasms) are most common in the pediatric age group, and they are often treated with intermittent doses of antibiotics and steroids, beta blockers, and more recently beculizimab in conjunction with the judicious use of surgery. In a recent review from 2011 on the use of propranolol for infantile hemangioma, 58.8% of 85 cases were treated with a dose of 2 mg/kg per day. Improvement or complete resolution of the lesion was noted in 96%, with recurrences in only one-fifth of cases. ⁴ In another study, of 42 patients with cavernous hemangiomas of the orbit, all treated surgically, 83% achieved good visual function. ⁵ In general, localized benign orbital lesions can and probably should be safely removed, with vascular neoplasms perhaps being the one exception where a trial of medication is indicated, particularly for obvious hemangiomas or those vascular anomalies that are microscopically and radiographically microcystic.

13.5.2 Primary Malignant Tumors

Malignant Vascular Tumors

Malignant vascular tumors within the orbit include hemangiopericytomas, angiosarcomas, and Kaposi’s sarcomas (this last lesion is included here rather than with the mesenchymal tumors). As a rule, vascular malignant tumors within the orbit are rare with angiosarcoma in the orbit as a primary neoplasm is extremely rare. ⁶ Few if any centers have more than simple case reports to share on the subject. The treatment of malignant vascular tumors within the orbit has included surgery with complete resection whenever possible, as well as with adjuvant radiotherapy. As these lesions develop nests of malignant cells running along blood vessels, often outside the palpable boundary of the neoplasm, obtaining negative margins can sometimes be challenging. Careful preoperative counseling with approval for enucleation or orbital exoneration when necessary is an important part of the preoperative evaluation. It must be borne in mind that while the orbit may be preserved, loss of bony support can often present additional changes to functional vision due to enophthalmos, diplopia, and loss of the upper and lower eyelids. In addition, adjuvant radiotherapy also carries significant risk of injuring the lens, the optic nerve, and the retina, which can cause intractable treatment pain and/or blindness. This is one of several critical reasons why thorough multidisciplinary input and planning agreement upon therapeutic plan must precede initiation of treatment. All of the oncologic specialties involved must be “on the same page.”

Neogenic Tumors

Retinoblastoma

Retinoblastoma is a neuroendocrine tumor and the most common orbital tumor in children, often being evident before 1 year of age. ⁷ Although most cases are sporadic, as many as 40% are genetic via an autosomal dominant gene that predisposes the patient to additional primary tumors such as sarcomas. It has been demonstrated that small tumors (those that are confined the retina) have a more favorable prognosis than larger tumors that extend outside the orbit or involve the optic nerve. Unfortunately, many patients do not present until metastasis or direct brain extension occurs. Some authors have proposed avoiding the use of fine needle aspiration to make the diagnosis in the case of retinoblastoma due to the fear of seeding the tumor within the orbital fat. The offending gene mutation is reported to be at the 13q14 locus of the chromosome, with possession of one normal gene copy offering protection. ⁷ Histologically, three distinct patterns have been described. The first pattern is completely undifferentiated with extensive necrosis and a high mitotic rate. This subtype has the worst prognosis. The second type, containing “Homer–Wright rosettes” (cuboidal cells arranged around a central lumen), and a third type containing “fleurettes” (where the retinoblasts are arranged in an organized pattern reminiscent of the “fleur-de-lis”) are both considered to offer a better prognosis. ⁷ This malignancy is often devastating due to the age of onset and the common need for multimodal therapy, including definitive or adjuvant radiotherapy, which can inhibit craniofacial growth and induce second malignancies despite curative treatment of the retinoblastoma. It is hoped that, with the increasing availability of proton beam therapy, the morbidity associated with treating young children with orbital retinoblastoma can be reduced.

Rhabdomyosarcoma

Rhabdomyosarcoma is overall the most common orbital malignancy, with most cases occurring in children less than 10 years of age, though it can be relatively common up to 20 years of age. ^{8,​ 9} It is the most common sarcoma that occurs in the head and neck region; according to the Intragroup Rhabdomyosarcoma Study (IRS), the head and neck was the location of over one-third of all cases, with most of those occurring in the orbit. ¹⁰ Rhabdomyosarcoma also occurs in the middle ear and mastoid region, nasal cavity, nasopharynx, paranasal sinuses, and occasionally the infratemporal fossa. The differential diagnosis may include hemangiomas, neurofibromas, and optic nerve gliomas as well as more common inflammatory conditions. Growth can be rapid, with the appearance of proptosis with or without visual loss over one or two days. ⁸ Fine needle aspiration can generally make the diagnosis, often with the assistance of ultrasound. CT and MRI in combination are recommended to assist with staging and treatment planning. Several histological subtypes have been described for rhabdomyosarcoma including embryonal, botryoid (a variant of embryonal), alveolar, and pleomorphic. Most orbital tumors (95%) belong to the embryonal/botryoid variant, with the remainder of the orbital tumors being of the alveolar type. The embryonal variant tends to be better differentiated but occasionally presents in a poorly differentiated pattern with very few rhabdomyoblasts. Cells are often spindle-shaped or fusiform with an elongated nucleus and tapered ends. Mitoses are common. The botryoid (“bag of grapes”) variant is common in small children under 5 years of age and typically presents with grapelike structures associated with hollowed areas such as the nasal cavity, and may be mucosa-covered. The botryoid variant carries the best prognosis.

Alveolar rhabdomyosarcomas are usually found in slightly older children, such as teenagers or young adults. Histologically, tumor cells are arranged in an alveolar pattern centrally attached to a fibrous septum. Often special stains to identify myogenesis within the cytoplasm are necessary or even critical for making the diagnosis. The pleomorphic variant is the least common and is almost always a disease of the extremities in adults. Light microscopy can usually demonstrate striated muscle differentiation, and the diagnosis can be assisted by positive stains for desmoid muscle–specific actin and myoglobin. ^{11,​ 12} It is noteworthy that S100 and cytokeratin stains are occasionally positive in some rhabdomyosarcomas. The alveolar rhabdomyosarcoma has been linked to a chromosomal rearrangement t(2;13)(q35; q14), ^{13,​ 14} While embryonal rhabdomyosarcomas may be linked to the loss of heterozygosity on chromosome 11, carefully identifying the histological subtype has prognostic significance, with the botryoid variant doing better than the embryonal variant, which has a better prognosis than the alveolar variety. The 5-year overall survival ranging between 20 and 83% is dependent upon the respective group.

Treatment is generally initiated with concurrent radiation and chemotherapy. While prompt surgery is not necessarily wrong, aggressive tumors may recur before adjuvant radiotherapy and chemotherapy can be initiated. Surgery is therefore generally reserved for a salvage role or when there is residual tumor following chemoradiotherapy.

Optic Nerve Glioma

The optic nerve glioma is essentially an astrocytoma of cranial nerve II. The ascending cell is the fibrillary astrocyte that exists in the oligodendroglioma supporting fascia that exits the brain with the optic nerve. ⁹ These lesions represent only about 2% of orbital tumors, often occurring in patients with neurofibromatosis. ³ Only about 20% are purely intraorbital with most extending up to or involving the optic chiasm. ^{2,​ 9} The lesion tends to grow slowly and run a fairly benign course in children and young adults. The lesion often attains considerable size before total visual loss is evident. In very young children, however, or in mature adults, the optic nerve glioma can be a fairly aggressive lesion, demonstrating rapid growth and progressive loss of vision. The diagnosis can often be made radiographically due to the homogeneous fusiform dilatation evident of the optic nerve on CT scan. Slowly progressive proptosis with gradual loss of vision is the key presenting symptom. The tumor is not considered to be particularly chemosensitive or radiosensitive and the treatment approach is generally surgical through a frontal orbital craniotomy (see Chapter ▶ 12).

Less common lesions including malignant schwannomas and non–optic nerve neuroblastomas. These often involve sensory nerves within the superior orbital fissure and can be quite aggressive, commonly extending intracranially. These lesions often initially present with distant metastases. Postoperative radiotherapy is all but universally indicated in this setting for these uncommon aggressive tumors.

Meningiomas

Meningiomas within the orbit account for approximately 5% of orbital tumors. ¹⁵ Generally considered benign, meningiomas in the orbit can involve the optic nerve or can directly spread from an intracranial meningoma through the superior orbital fissure ( ▶ Fig. 13.5). It is occasionally difficult to know whether the tumor began intracranially and grew downwards. Most have a benign course and are occasionally recognized incidentally and can simply be monitored. Occasionally, however, an intraorbital meningioma can be aggressive, requiring combined transorbital and transcranial approaches for complete excision (see Chapter ▶ 12).

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