[Primitive cutaneous Ewing's sarcoma: a diagnostic and therapeutic dilemma]

Ewing's sarcoma (or peripheral neuroectodermal tumour) is generally found in bone tissue, and a primary dermal site is extremely rare. We report a case of primary cutaneous Ewing's sarcoma in a 21-year-old woman.

A 21-year-old woman presented with a scapular lesion that had been slowly developing for one year. The 1-cm lesion was removed and histological examination showed proliferation of small round cells in the dermis. Immunostaining revealed cytoplasmic membrane expression of CD99 and a negative immunoprofile for other small round-cell tumors. Ewing's sarcoma fusion gene transcripts were detected using fluorescence in situ hybridization (FISH). A staging examination revealed no other abnormalities. It was decided to treat the lesion as for osseous Ewing's sarcoma with wide resection followed by systemic adjuvant chemotherapy.

Cutaneous Ewing's sarcoma raises concerns about diagnosis and treatment. Owing to the non-specificity of its clinical presentation, histology and immunoprofile, diagnosis of superficial Ewing's sarcoma is difficult and numerous differential diagnoses must be considered. When dealing with a surface tumour, the diagnosis of cutaneous Ewing's sarcoma must be considered. CD99 immunostaining and molecular testing for evidence of EWSR1 rearrangement are useful investigations to confirm the diagnosis. Furthermore, modalities of treatment must be carefully discussed. Cutaneous Ewing's sarcoma is currently treated in the same way as osseous Ewing's sarcoma (wide surgical excision, adjuvant radiotherapy when surgical margins are unsatisfactory, systemic adjuvant chemotherapy, and, in some cases, bone marrow transplant). However, some studies show a more favourable prognosis for cutaneous Ewing's sarcoma than for osseous Ewing's sarcoma. We may thus ask whether such aggressive multimodal treatment is needed.