Cutaneous Clear Cell Sarcoma

Abstract

Clear cell sarcoma is a unique soft tissue tumor with distinct microscopic features that include a nested or fascicular pattern of spindle cells accompanied by larger wreath-like giant cells scattered throughout. It harbors a unique EWSR1-ATF1 gene fusion secondary to a t(12;22)(q13;q12) translocation. Recently, it was reported that clear cell sarcoma can occur in the skin and mimic a broad spectrum of entities, including spindle cell melanoma. Here, we describe 3 new cases of clear cell sarcoma of the skin, all of which were confirmed molecularly. The patients, a 12-year-old boy, a 29-year-old woman, and a 60-year-old man, had cutaneous lesions on the thigh, dorsum of foot, and sole, respectively. All 3 lesions were originally considered suspicious of spindle cell melanoma. Microscopically, the lesions featured nodular proliferation centered in the dermis that consisted of discrete fascicles of spindle cell enmeshed by thin fibrous strands. Wreath-like cells were present in all cases. Tumor cells were positive for S100 protein (3 of 3 cases), melan A (2 of 3 cases), HMB 45 (1 of 3 cases) although a junctional melanocytic proliferation was seen in 1 case. Sentinel lymph node biopsy was negative in 2 patients. Follow-up was uneventful in 2 patients, whereas the other patient developed a lymph node metastasis 5 months after primary tumor excision. This study confirms that malignant dermal tumors that mimic but do not exactly replicate spindle cell melanoma should raise suspicion for cutaneous clear cell sarcoma and prompt the investigation for the confirmatory gene fusion t(12;22).