A soft tissue sarcoma (STS) is a malignant tumor that starts in soft tissue such as muscle, deep skin tissues, cartilage, or fat. It often occurs as a lump in the arm, although it can happen anywhere.

Dear Dr. Gott: I am a 70-year-old white male. Approximately four years ago, I developed a "fatty tumor" in my upper right chest area, which was surgically removed in January 2003. These fatty tumors ...