Superficial primitive Ewing's sarcoma: a clinicopathologic and molecular cytogenetic analysis of 14 cases.

Superficial primitive Ewing's sarcomas are rare and have been reported to be of favorable prognosis compared to conventional deep-seated tumors. In the skin and subcutis, the diagnosis is often difficult, and performing molecular cytogenetic techniques may be helpful. We performed a retrospective analysis of 14 cases of superficial Ewing's sarcomas, all confirmed by molecular cytogenetics. Clinical, histological, immunohistochemical, molecular cytogenetic, therapeutic, and follow-up data are reported. There were 11 female and 3 male patients aged from 12 to 77 years (median: 17 years). Seven tumors occurred in the extremities, five in the trunk wall, and two in the head. Tumor size ranged from 1 to 5 cm (median, 3 cm). They were all small round-cell proliferations with a strong membranous positivity for CD99. Ewing's sarcoma translocations/fusion gene transcripts were detected in eight cases, both by FISH and reverse transcriptase (RT)-PCR. Four tumors were positive by RT-PCR alone (FISH not done in three cases and not interpretable in one case), and two cases were positive by FISH alone (RT-PCR not done). Surgical resection was performed in all patients. Chemotherapy was given in ten patients and radiotherapy in six. At last medical examination (median follow-up, 47 months), two patients who underwent surgical resection alone had died from the tumor. Our results confirm that superficial Ewing's sarcomas are of good prognosis. Given the difficulty of the diagnosis and the importance of an adapted treatment, a confirmation of the diagnosis by molecular or cytogenetic techniques is recommended when dealing with a superficial tumor.