Presence of well-differentiated rhabdomyoblasts at the end of therapy for pelvic rhabdomyosarcoma: Implications for the outcome

The presence of well-differentiated rhabdomyoblasts at the end of therapy f or rhabdomyosarcoma has been noted. This study was undertaken to investigat e the therapeutic implications of the presence of well-differentiated rhabd omyoblasts at the end of therapy for pelvic rhabdomyosarcoma. Six patients with pelvic rhabdomyosarcoma (bladder-prostate, 4; vulvovaginal, 2) with di sease diagnosed between the years 1974 and 1992 were sequentially investiga ted by cystoscopic or vaginoscopic examination and biopsy during and after completing therapy. All six patients received treatment according to prevai ling therapeutic protocols. Biopsy material from all six patients at the en d of therapy documented the presence of well-differentiated rhabdomyoblasts . Repeated biopsies demonstrated the presence of rhabdomyoblasts; however, they appeared to decrease in number with lime. Mitotic activity was not obs erved in the biopsy materials obtained. All six patients are alive without evidence of disease from 37 to 233 months after therapy ended. The presence of well-differentiated rhabdomyoblasts at the end of therapy for pelvic rh abdomyosarcoma is a common finding. The biologic nature of these well-diffe rentiated rhabdomyoblasts is not completely known, but they do not appear t o connote the persistent presence of malignant disease and are not an indic ation for the continuation of therapy.