Epithelioid hemangioendothelioma after radiotherapy for congenital hemangioma: a case report.

A rare case of post-radiation epithelioid hemangioendothelioma arising in a congenital hemangioma of the lower leg 18 years after radiotherapy is reported. At 7 years of age, the patient underwent partial resection of a subcutaneous congenital hemangioma with intramuscular extension of the left lower leg, and at 10 years of age, the patient was given radiotherapy with a total dose of 30 Gy for recurrence. At 28 years of age, the patient noticed a large tumor mass with intractable pain at the antero-lateral aspect of the proximal lower leg, and she presented to our hospital. Since microscopic examination of a biopsy specimen showed epithelioid hemangioendothelioma, disarticulation at the knee joint was performed. Although malignant change in a benign vascular tumor is extremely rare, irradiation can induce malignant transformation of a hemangioma.