Abstract

A case of postirradiation extraskeletal osteosarcoma with aggressive fibromatosis of the overlying soft tissue of radiation field is reported in a 57 year old house wife who was treated with operation and radiation therapy for cervix carcinoma of the uterus 23 years ago. The overlying aggressive fibromatosis showed characteristic radiation angiitis and atrophic vascular changes such as hyaline degeneration and obliteration of the capillaries which were highly campatible with radiation changes. She also had multiple osteogenic sarcoma in pelvic cavity, occurring in the mesentery bed. As for the histogenesis in this case, we thought the possiblity that fibroblasts went through a process of differentiation into osteoblasts that were responsible for bone formation in the process of malignant change of the aggressive fibromatosis.