Posters— Diagnostic Imaging/Pathology

MALIGNANT FIBROUS HISTIOCYTOMA ARISING WITHIN A SOLITARY OSTEOCHONDROMA

Carluke I, A Grainger, Murray SA, Malcolm AJ (The North of England Bone and Soft Tissue Tumour Service, The Freeman Hospital, Newcastle upon Tyne, U.K., NE7 7DN)

Malignant change of exostoses in patients who have multiple osteochondromas is well recognised. Chondrosarcoma is most commonly seen, although osteosarcoma and other soft tissue sarcomas have been described. Malignant fibrous histiocytoma arising within an exostosis in a patient who had multiple osteochondromas has been reported in the literature. We report an almost unique case of MFH occuring within a solitary osteochondroma arising from the proximal tibia of a 21 year old male. This was treated by en bloc excision, with allografting of the resultant defect. Pathological examination and immunohistochemical staining showed a focus of hypercellular spindle cell tumour embedded in a collagenous matrix, with marked positivity to SMA, within co-existent osteochondroma and bursa.