According to the American Cancer Society, soft tissue sarcoma is a type of cancer that begins in fat and deep skin structures, muscle, blood vessels and nerve and fibrous tissues. Although sarcomas aren’t common, they usually develop in the abdomen, arms and legs. Not all soft tissue sarcomas are malignant.
Soft tissue sarcomas present in about 50 different forms, such angiosarcoma, which starts in the blood or lymph vessels, and Kaposi's sarcoma, which starts in cells lining the lymph or blood vessels. Some sarcomas are age-specific, and they grow in the soft tissues, including connective tissues such as tendons or the linings of joints.
According to the Mayo Clinic, unlike other tumors, soft tissue sarcomas may not present with any symptoms until they grow large enough to cause a noticeable lump. Further, soft tissue sarcomas can become painful if they press on a nerve or muscle.
Risk factors for developing soft tissue sarcoma include radiation therapy for certain cancers and exposure to chemicals such as thorium dioxide, vinyl chloride and arsenic. Also, certain hereditary genetic disorders such as retinoblastoma, Werner syndrome and Bourneville disease can predispose people to soft tissue sarcoma.
Tests for soft tissue sarcoma include MRI, CT and PET scans. In addition, doctors may perform a biopsy to take samples of a lump or tumor.