A case of low-grade fibromyxoid sarcoma of the thigh

A case of low-grade fibromyxoid sarcoma in the thigh of a 21 year old female is described. The patient had a fist-sized well-defined mass in her left thigh that enlarged over a 6 month period. Histologically, the neoplasm showed contrasting fibrous and myxoid areas with a swirling growth pattern. Cellularity was low to moderate, and the stromal cells were benign looking without mitoses or nuclear pleomorphism. The tissue was not noticeably vascular. Some stromal cells were aggregated around the blood vessels. The stromal cells were immunoreactive to vimentin, but were negative to keratin, desmin, alpha-smooth muscle actin, actin HHF35, S-100 protein, neuron-specific enolase, and epithelial membrane antigen. Ultrastructural examinations of the stromal cells revealed well-developed rough endoplasmic reticulum, mitochondria, pinocytotic vesicles, and numerous intermediate-sized filaments in the cytoplasm. These findings seem to indicate that the stromal cells were fibroblastic in origin. The occurrence of the tumor in a young adult, its location and its large, well defined borders together with the characteristics revealed through histological investigation, indicated that it was in fact what has been termed by Evans as a low-grade fibromyxoid sarcoma.