The main tumors of bone are the benign osteoma and the malignant osteosarcoma (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23). Osteoma is the most common tumor of the nose and paranasal sinuses and the most common neoplasm of the frontal sinus. Osteoma that arises from the bones of the frontal sinus, ethmoid sinus, and other periorbital bones can extend into orbit. Osteoma in an ocular oncology practice are relatively uncommon (2,3,4,5,6). In the authors’ series of 1,264 orbital lesions, the 4 osteomas accounted for 19% of osseous and fibro-osseous tumors and for ,1% of all orbital tumors. The true incidence is actually greater, because most lesions originate in the sinuses, have minimal orbital involvement, and are more likely to be managed by otorhinolaryngologists.

Orbital osteoma can sometimes occur with Gardner syndrome, an autosomal-dominant condition characterized by adenomatous polyposis of the bowel, secondary bowel cancer, typical congenital hyperplastic lesions of the retinal pigment epithelium (RPE), desmoid tumors, and other lesions (8,18). The RPE lesions are discussed in the Textbook and Atlas of Intraocular Tumors. A patient with a suspected orbital osteoma should undergo ophthalmoscopy and possible referral to a gastroenterologist.

Orbital osteoma can occur at any age and there is no predilection for gender. Depending on the size and location of the osteoma, it can be asymptomatic or can produce orbital symptoms and signs such as proptosis and displacement of the globe. Osteoma can cause pain, described by the patient as a headache. A hard mass may be visible and palpable at the superior or nasal orbital rim. The bony mass may obstruct the ostea of the sinus and lead to chronic sinusitis or secondary mucocele.

Computed tomography of orbital osteoma shows a sessile or pedunculated mass with bone density arising from otherwise normal bone, usually the frontal or ethmoid bones. The ivory type may be identical to bone; the fibrous type is less dense and may resemble fibrous dysplasia.

Histopathologically, osteoma has been divided into three types: compact (ivory), cancellous, and fibrous (1,2,3,4). It is believed that the compact type is most mature and the fibrous the least mature and that the fibrous type may be part of a continuum incorporating ossifying fibroma and fibrous dysplasia (1,3).

Asymptomatic orbital osteoma can sometimes be followed conservatively. The only exception is an osteoma of the sphenoid bone that shows encroachment on the optic canal, in which case earlier surgical excision may be justified. A larger or symptomatic osteoma can be managed by surgical excision. A superonasal lynch incision can be used for the more common superonasal lesion. For a more posterior osteoma that involves the orbital roof or cribriform plate, a combined orbitocranial approach can be employed. Bone instruments are required for this surgery. Incomplete removal does not usually lead to recurrence (4).

Whitson W E, Orcutt JC, Walkinshaw M D. Orbital osteom a in Gardner’s syndrome. Am J Ophthalmol 1986;101:236-241.

Osteosarcoma (osteogenic sarcoma) is the most common primary malignant neoplasm of bone. It occurs twice as frequently as chondrosarcoma and three times more often than Ewing sarcoma (1). It is a neoplasm of children or young adults that usually originates in long bones and rarely from flat skull bones.

Osteosarcoma can affect the orbital bones as a primary lesion or as a secondary tumor after irradiation for familial retinoblastoma (1,2,3,4,5,6,7,8,9,10,11,12). It has an increased incidence in patients with Paget disease and fibrous dysplasia (4,5,6,7). There is a close genetic relationship between osteosarcoma and retinoblastoma, with both being linked to a deletion in the long arm of chromosome 13 (3). In the authors’ series of 1,264 orbital lesions, the 5 osteosarcomas accounted for 24% of osseous and fibro-osseous tumors and 1% of all orbital tumors (8). All 5 osteosarcomas in our series occurred in patients who had undergone ipsilateral orbital irradiation for hereditary retinoblastoma (11). We had no case of primary orbital osteosarcoma (8).

Primary orbital osteosarcoma characteristically causes a rapid onset and progression of unilateral proptosis, pain, globe displacement, periorbital numbness, eyelid edema, and conjunctival chemosis (7). When the tumor arises from the ethmoid or frontal bones, there is downward or lateral displacement secondary to a firm, palpable, mass, whereas one arising from the sphenoid wing causes proptosis without a palpable mass.

Orbital CT and magnetic resonance imaging (MRI) generally show an irregular, invasive, destructive bone mass with foci of calcification and invasion of adjacent soft tissue. If the osteoid content is low and the fibrovascular content high, then the lesion appears less dense than bone. In some cases, linear shadows radiate from the main mass because tumor cells grow in fingerlike projections from the main mass. CT shows the bony extent of the lesion; MRI can better delineate the soft tissue component.

Orbital osteosarcoma is composed of malignant spindle cells with hyperchromatic nuclei and numerous mitotic figures. Osteoid and neoplastic bone formation are readily evident. If there are no bone elements, the lesion is more likely to be diagnosed as a fibrosarcoma (7). In many cases, the matrix of the tumor contains chondroid and fibromatoid elements and numerous blood vessels. Thin-walled sinusoidal spaces may contain neoplastic cells, perhaps accounting for the blood-borne metastasis.

Osteosarcoma involving the orbital bones poses a difficult therapeutic challenge. Some authorities advocate preoperative chemotherapy, followed by wide surgical excision, and subsequent chemotherapy or irradiation depending on the clinical and histopathologic findings. The prognosis for patients with osteosarcoma of the orbital bones is generally poor and, historically, most patients have died despite treatment (7).

Several fibro-osseous lesions can occur in the orbital bones, including fibrous dysplasia, ossifying fibroma, aneurysmal bone cyst, giant cell tumor (osteoclastoma), giant cell reparative granuloma, and brown tumor of hyperparathyroidism. Most of these are discussed in more detail elsewhere (1,2,3,4) and are not covered in detail here.

Fibrous dysplasia, a fibro-osseous malformation that presumably results from an idiopathic arrest in the maturation of bone at the woven bone stage, can sometimes involve the orbital bones (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22). It may be monostotic or polyostotic. The monostotic form accounts for 80% of cases, of which 20% affect the craniofacial bones. The frontal bone is most often involved, followed by the sphenoid and ethmoid bones. Orbital fibrous dysplasia is generally of the monostotic form, although it usually involves contiguous bones (3). The polyostotic form occasionally is found as a part of Albright syndrome, characterized by precocious puberty in girls and mottled skin pigmentation ipsilateral to the osseous involvement. Orbital cases are rarely associated with Albright syndrome (21,22).