Primary Clear Cell Sarcoma of the Breast: A Case Report

Abstract

Abstract Casestudy: Clear cell sarcoma (CCS), also known as malignant melanoma of soft parts, is a primary soft tissue neoplasm exhibiting evidence of melanocytic differentiation. It is an uncommon aggressive tumor that arises in tendons and aponeuroses of the distal extremities. Here, we report the first case of primary CCS of the breast. The patient was a 43-year-old female who presented with a left breast mass and underwent surgical resection at an outside hospital. No history of melanoma or any other malignancies was reported. Grossly, it was described as a 2 x 1.5 x 1.5 cm, well-demarcated, white nodular mass. Microscopic examination showed a malignant neoplasm composed of short spindle cells with ill-defined, eosinophilic cytoplasm and ovoid nuclei with finely stippled chromatin and exhibiting moderate pleomorphism. The lesional cells were arranged in short interlacing fascicles with abundant collagen, with brisk mitotic activity (>15/10 HPF). The differential diagnosis included spindle cell carcinoma, myoepithelial carcinoma and melanocytic neoplasm. The tumor cells were immunoreactive for S-100 protein, SOX10, Mart-1, HMB45 and MiTF, but negative for multiple cytokeratins (including high and low molecular weight keratins), p63, EMA, CEA, Caldesmon, smooth muscle myosin, calponin, desmin, ERG, and CD31, thus confirming melanocytic origin. EWSR1 gene rearrangement was detected by fluorescence in situ hybridization analysis using break-apart probes. Overall, the histomorphology combined with the immunophenotype and cytogenetic characteristics, was most consistent with a CCS. To our knowledge, no primary CCS of the breast has been previously reported in the English language literature.