Soft tissue sarcoma - what to expect once diagnosed?

It depends...: You need to know the size and grade of your sarcoma or what was the name given to it. The prognosis is good for smaller tumors(less than 5cm) and for low/intermediate grade sarcoma. But if it was over 5 cm and high grade then there is substantial risk for relapse; so close surveillance is advised.

Surgery/radiation: Soft tissue sarcoma is treated primarily with surgery. Radiation is often added to lower risk of it growing back. It is controversial if chemotherapy helps. Some doctors give it and some do not. The cancer can grow back or spread after removal, so patients are checked periodically for many years. Amputation is required only rarely. The rest depends on the specifics of the case.