Clinical characteristics and surgical treatment of perianal and perineal rhabdomyosarcoma: analysis of Japanese patients and comparison with IRSG reports.

Rhabdomyosarcomas of the perianal and perineal regions are uncommon. This study was performed to clarify the clinical characteristics and guidelines of surgical treatment of patients with perianal and perineal rhabdomyosarcomas younger than 20 years of age. Twenty-nine patients, 26 patients identified in the Japanese literature and three of our own, were analyzed and the results were compared with the data reported from the Intergroup Rhabdomyosarcoma Study Group (IRSG). Female predominance and a twin-peak age distribution in infancy and adolescence were characteristic findings of the Japanese patients that were not observed in the IRSG studies. The demographic differences between the two groups were attributed to the differences in demographics of patients younger than 10 years of age. Of the 29 patients, 17 were categorized into clinical groups III/IV and 21 patients into stages 3/4. Alveolar histology was diagnosed in 18 patients. In patients more than 10 years of age, the female predominance was more prominent and the incidences of advanced clinical groups/stages and alveolar histology were significantly higher than those in patients younger than 10 years of age. Inguinal lymph nodes were always involved in patients with lymph node metastases and three patients developed metastases to the breast. Information regarding the survival time was available for 18 patients and the 5-year overall survival was 20%. Two patients with a group I/stage 2 tumor and one with a group II/stage 3 tumor survived for more than 2 years with no evidence of the disease. In these patients, the tumors were excised by primary surgery or primary reexcision and they were not accompanied by lymph node metastasis. Based on these data, complete tumor resection prior to chemotherapy should be pursued and the inguinal lymph nodes should be at least sampled because nodal involvement is closely associated with the patient's prognosis.