[header] How to diagnose sarcoma [title] Check for new or unexplained lumps on your body. [step] A lump could either be a cyst (benign) or a tumor (cancer). Even if the lump is small and does not feel painful when pressed, it could be cancerous. 
Pay a visit to your doctor and have it looked at. See your doctor right away if the lump is located : [substeps] Within a muscle.