Dictionary.net

A variety of sarcoma having a reticulated fibrous stroma enclosing groups of sarcoma cells, which resemble epithelial cells and are enclosed in alveoli walled with connective tissue. It is a rare tumor, usually occurring between 15 and 35 years of age. It appears in the muscles of the extremities in adults and most commonly in the head and neck region of children. Though slow-growing, it commonly metastasizes to the lungs, brain, bones, and lymph nodes. (From Dorland, 27th ed; DeVita Jr et al., Cancer: Principles & Practice of Oncology, 3d ed, p1365)