Benign soft tissue masses are 10 times more common than cancerous soft tissue masses, according to UW Medicine. Soft tissue masses are usually round in shape and can be soft or firm to the touch. Cancerous soft tissue growths, or sarcomas, are frequently painless, are likely to grow rapidly, and additional, smaller growths often accompany them. Benign tumors have a higher likelihood of being painful to the touch and are usually smaller due to their slower growth rate.
Although most soft tissue masses are not cancerous, unusual new growths require medical evaluation to ensure that they are not sarcomas. It is imperative to seek medical attention for masses that are 2 inches or longer because they have the highest probability of being malignant. A doctor may perform a biopsy of the tissue if he suspects that it is cancerous. A doctor should also examine a bruise that has lasted six weeks or longer to rule out the possibility of cancer. Doctors sometimes initially misdiagnose sarcomas as bruises or injuries, and this can lead to a delay of three to six months before doctors recognize malignancy, states UW Medicine.
Soft tissue masses are most likely to occur on the legs and arms. Seven to 10 percent of soft tissue sarcomas are synovial sarcomas, an aggressive cancer that, once metastasized, results in lethality for as many as 75 percent of patients within five years, says UW Medicine.