2017 Volume 31 Issue 3 Pages 280-284
A woman in her twenties visited our hospital presenting with a subcutaneous tumor on the back, which gradually enlarged to 5 cm in diameter over a year. A biopsy was performed with the provisional diagnosis of an epidermoid cyst. The tumor contained prominent mucinous fluid. A histological examination revealed the proliferation of small round tumor cells in an alveolar configuration. Immunohistochemistry studies found that the tumor cells were positive for vimentin and CD99, while cytogenetic studies revealed the reciprocal translocation t (22 ; 11) (q24 ; q12) and the fusion gene EWS/FLI-1. A systemic examination revealed no other lesions suggesting malignancy ; thus, we diagnosed the tumor as a primary cutaneous extraskeletal Ewing's sarcoma. We excised the tumor with a margin of 4 cm, and administered adjuvant chemotherapy to the patient. We found no recurrence or distant metastasis over a 3-year follow-up period. According to previous literature and as seen in the present case, primary cutaneous extraskeletal Ewing's sarcoma is very rare, although its prognosis is better than that of Ewing's sarcoma of the bone.[Skin Cancer (Japan) 2016 ; 31 : 280-284]
