an immature malignant tumor of connective tissue; a malignant variant of fibroma, fibromyoma (leiomyoma), or fibroadenoma that can occur in any part of the body. It is characterized by invasive and destructive growth but sometimes has distinct contours. In cross section it looks like fish flesh. A fibrosarcoma has a marked capacity to metastasize, chiefly through blood vessels. It can often be distinguished from a fibroma only by histological examination and is treated surgically.