Two cases of extraosseous Ewing's sarcoma/peripheral neuroectodermal tumor 
arising in unusual, superficial sites are reported. One tumor involved the 
vaginal wall of a 35-year-old woman, and the other neoplasm arose in the dermis 
of the vulva in a 28-year-old woman. The tumors showed characteristic 
microscopic features of Ewing's sarcoma/peripheral neuroectodermal tumor with 
nodular monotonous proliferations of undifferentiated, small, round, 
hyperchromatic cells with a low mitotic index. Rare rosette-like formations were 
apparent only in the vulvar neoplasm. The tumors displayed intense 
immunoreactivity in a membranous pattern for CD99, the cell surface glycoprotein 
encoded by the MIC2 gene. Genetically, the tumors expressed the EWS/FLI-1 
chimeric transcript, derived from the t(11;22)(q24;q12) chromosomal 
translocation. Both patients had localized disease treated with wide local 
excision; one received postoperative chemotherapy, and the other received 
chemotherapy and radiotherapy. To date, 18 and 19 months after diagnosis, 
neither patient has had clinical evidence of local recurrence or metastasis. To 
our knowledge, these are the first reported cases of vaginal and vulvar Ewing's 
sarcoma/peripheral neuroectodermal tumor, confirmed with molecular genetic 
analysis, in the English literature.