Exophytic Osteochondroma of the Brow.

Most bony and cartilaginous lesions of the orbit and periorbital compartments are benign, grow endophytically, and are composed of dense lamellar bone (eburnated or ivory osteomas). An 87-year-old woman had a well-circumscribed, firm, round, and exophytic lesion of the brow region for at least 15 years. Excisional surgery disclosed an osteocartilaginous lesion with an enveloping pseudocapsule (periosteum/perichondrium) and a narrow stalk connecting it to the frontal bone. The periphery of the lesion displayed lamellar bone which appeared to be replacing a central cartilaginous zone. The adjacent deep preaponeurotic fat displayed nodules of collagen with myxoid change and occasional CD34 spindle cells suggestive of a spindle cell lipoma. Because of the osteochondroma's deep location in the preaponeurotic fat, the lesion differs from an osteoma cutis found in the dermis which fails to exhibit a cartilaginous component or a periosteum. Other clinically simulating lesions are described.