Osteochondroma (Exostosis) is the most common benign tumor of the bone. It may occur as solitary or multiple lesions and most commonly affected age group is 11-20 years. Its common complications include cosmetic or osseous deformity, fracture, neurovascular compromise, bursa formation and malignant transformation. Latter is the most serious and feared complication occurring mostly in third to fifth decade. The risk of malignant progression is estimated to range from 1 to 25% in patients with multiple osteochondromas. In this study, we present a case of high grade chondrosarcoma which was diagnosed cytologically in a 27 year old male with multiple osteochondromas. Cytological smears were cellular showing atypical cells with marked
pleomorphism in a background with chondromyxoid material. Subsequent histopathology of the lesion confirmed the diagnosis. Through this case report we wish to highlight that FNAC is very effective in confirming preoperative diagnosis of chondrosarcomatous transformation in osteochondroma.

Keywords: Multiple Osteochondromas(MO); Chondrosarcoma; FNAC.