Two unusual osteogenic orbital tumors - Presumed parosteal osteosarcomas of the orbit

Objective: To report two cases of suspected parosteal osteosarcoma of the o rbit, with dedifferentiation into a high-grade liposarcoma occurring in one patient. Design: Two retrospective case reports. Methods. The clinical, radiologic, and pathologic records of two patients w ith suspected orbital parosteal osteosarcoma were retrospectively reviewed. Main Outcome Measures: Histologic evaluation and clinical follow-up were me asured. Results. The first patient was a 47-year-old male presenting with a 5-month history of painless right lower lid swelling; excision biopsy suggested a well-differentiated parosteal osteosarcoma of the orbital floor, which recu rred 3 years later. Six months after excision of the recurrence, the mass d emonstrated accelerated growth, and a lid-sparing exenteration was performe d; histologic examination showed a high-grade liposarcoma. The patient rema ins disease-free at 4 years. The second patient, a 40-year-old male, presen ted with an 8-year history of proptosis and a right superotemporal orbital mass. The mass was excised completely at lateral orbitotomy; histologic exa mination suggested a well-differentiated parosteal osteosarcoma. The patien t remains well 9 months postoperatively. Conclusions: Parosteal osteosarcoma is an uncommon tumor, usually affecting long bones, that is extremely rare in the orbit. It is a low-grade sarcoma that tends to recur locally after excision but has a favorable prognosis. Dedifferentiation into a high-grade sarcoma occasionally occurs in parostea l osteosarcoma, but transformation into liposarcoma does not seem to have b een previously reported. It is important to recognize dedifferentiated paro steal osteosarcoma, because the prognosis is poor, and radical treatment ma y be required. Ophthalmology 2001;108:1452-1456 (C) 2001 by the American Ac ademy of Ophthalmology.