Small cell osteosarcoma of bone, which was first described in 1979, is an unusual variant of osteosarcoma. Osteoid production by tumor cells is frequently focal or minimal, making the differential diagnosis with other small round cell tumors of bone difficult. Here, we present a rare case of small cell osteosarcoma of the mandible appearing as bony bulging mass in 31-year-old male who has neither tenderness nor paresthesia. Histologically, the tumor contains hypercellular cartilage and abnormal osteoid associated with small round to ovoid malignant cells. Awareness of small cell osteosarcoma should be emphasized because it has worse prognosis than both other small round cell tumor and conventional osteosarcoma.

• 양동현(연세대학교 치과대학 구강병리학교실, 구강종양연구소) | Dong Hyun Yang
• 김형준(연세대학교 치과대학 구강악안면외과학교실) | Hyung Jun Kim
• 박혁(연세대학교 치과대학 구강악안면방사선학교실) | Hyok Park
• 양우익(연세대학교 의과대학 병리학교실) | Woo Ick Yang
• 김현실(연세대학교 치과대학 구강병리학교실, 구강종양연구소) | Hyun Sil Kim correspondence