A sarcoma is a rare form of cancer affecting two types of connective tissues in the body. Soft tissue sarcoma invades cartilage, tendons, muscles and blood vessels. Osteosarcoma is found in the bones and is the rarest type, according to WebMD.
Symptoms of a sarcoma typically do not occur in the early stages. As the tumor progresses and becomes palpable, the patient may have localized pain and swelling. If the lump is around the stomach, a feeling of fullness is often felt, as stated by Cancer.Net.
People with a genetic disorder, such as neurofibromatosis, have an increased risk of developing sarcomas. Other risk factors include a family history of the disease and radiation exposure, as stated by WebMD.