Primary clear cell sarcoma of the sacrum: a case report.

Clear cell sarcoma, first described by Enzinger in 1965, is an uncommon malignant soft tissue neoplasm that displays melanocytic differentiation. It occurs predominantly in the soft tissue of the extremities in young adults or children. Primary clear cell sarcoma of the bone is extremely rare, only seven cases have been reported to our knowledge. We present here a case of a huge primary clear cell sarcoma of the sacrum arising in a 25-year-old man. The average percentage of melanin content in the tumor was 9.25 ± 6.71%, which resulted in hypointense signal in T2-weighted and heterogeneous hyperintense signal in T1-wieghted images of magnetic resonance imaging (MRI). The patient was treated with curettage of the mass and neither further radiotherapy nor chemotherapy had been provided. The patient had local regrowth of tumor at 9 months after surgery. To our knowledge, this is the first case of CCS in the axial skeleton documented in English literature.