Primary Ewing sarcoma of the penis in an adult man: First reported case in France.

Extra-skeletal Ewing sarcoma (EES) is an extremely rare condition, with only 10 cases reported worldwide. The challenge in this case remains the diagnosis, which relies on immunohistochemical and molecular testing: small round blue cells, CD99-positive expression and the presence of an EWSR1/FLI1 gene fusion. We herein report a 43-year-old male with a primary penile Ewing sarcoma, without apparent symptoms, and whose tumor type was difficult to identify on biopsy, with no definite histological diagnosis established before final surgery. A partial penectomy and adjuvant chemotherapy with vincristine, doxorubicin, and cyclophosphamide alternating once every 2 weeks with ifosphamide and etoposide were performed, with no recurrence at one year. This case highlights the importance of initial management of tumors of undetermined type, where complete surgical treatment is key to improving disease-free survival (DFS). To our knowledge, this is the first reported case in France.