Chondroblastic osteosarcoma of the temporal region: a diagnostic dilemma

Chondroblastic osteosarcoma (OS) accounts for about 25% of all cases of OS. It can pose diagnostic difficulty on cytology, as the tumor cells may resemble the carcinomatous cells. We present a case of a 35-year-old female patient who presented with a firm swelling in the left temporal region. On fine-needle aspiration, the smears revealed abundant cellularity with tumor cells showing significant nuclear pleomorphism and multinucleation. The tumor cells had abundant foamy to vacuolated cytoplasm, thereby indicating sebaceous differentiation and it was cytologically interpreted as sebaceous carcinoma. However, on subsequent histopathology, similar tumor cells were seen lying down abundant amount of osteoid material along with foci of chondroid differentiation and was diagnosed as chondroblastic OS. Pitfalls in the cytodiagnosis of this case along with differential diagnosis on cytology are discussed.