[490] Cutaneous Clear Cell Sarcoma: A Study of 3 Additional Cases with Molecular Confirmation

Giovanni Falconieri, Bostjan Luzar, Carlos E Bacchi. General University Hospital, Udine, Italy; University of Ljubljana School of Medicine, Ljubljana, Slovenia; Consultoria em Patologia, Botucatu, Sao Paulo, Brazil

Background: Clear cell sarcoma (CCS) is a distinctive soft part tumor showing some morphologic and immunophenotypic overlapping with melanoma, hence its time-honored designation of "melanoma of soft parts". Yet, CCS possesses distinctive microscopic features allowing its recognition, including an organoid, spindle cell pattern along to scattered larger “wreath-like” cells. In addition it harbors a unique EWSR1-ATF1 gene fusion secondary to the t(12;22)(q13;q12) translocation. Recently, CCS have been reported to occur in the skin where it may simulate a broad spectrum of entities, including spindle cell melanoma. In this study we describe 3 new cases of CCS of the skin with confirmatory molecular study.
Design: Three cases of cutaneous CCS were retrieved. The patients were a 12 year-old boy, a 29 year-old woman and a 60 year-old man complaining of nodules occurring in the foot, plant and thigh skin respectively, originally deemed suspicious of spindle cell melanoma. A panel of antibodies against cytokeratins, S100 protein, gp100, and melan A was applied to all cases. In addition all the cases had been tested for the EWSR1-ATF1 gene fusion/t(12;22)(q13;q12) translocation.
Results: Microscopically all the lesions were nodular proliferations centered in dermis featuring an organoid, spindle cell pattern along to scattered larger “wreath-like” cells. Fibrous septa were recognized. One case was associated with junctional focal melanocytic proliferation. Loose spindle cell nodules with a neuroid appearance were occasionally noticed. A low to moderate mitotic activity was observed as well. Tumor cells were positive for S100 protein (3/3) and gp100 (1/3). FISH analysis demonstrated chromosomal translocation t(12;22) to be present in >80% of tumor cell nuclei. Sentinel lymph node biopsy was negative in 2 patients. Follow up was uneventful in 2 patients; 1 patient developed a lymph node metastasis 5 months after primary tumor excision and was lost to follow up after one year.
Conclusions: Data from our study confirm evidence that malignant dermal tumors similar but not conforming to spindle cell melanoma should raise the suspicion of CCS and prompt investigation of confirmatory gene fusion t(12;22). Although actual patient management does not differ from that of melanoma, including conservative cutaneous excision and possibly a sentinel lymph node biopsy, the distinction between these conditions is especially warranted by the perspective of tailored patient management.
Category: Dermatopathology

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 94, Tuesday Morning


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