During a 2-week period, a 9-year-old girl developed a tender, dark red, centrally ulcerated 3 cm tumor on her left thigh, associated with inguinal lymphadenopathy. Histologic and immunohistopathologic evaluation disclosed a Ki-1+ large-cell anaplastic lymphoma. The patient received multiagent chemotherapy followed by autologous bone marrow transplantation and is in her second remission.