[Soft tissue sarcoma: how can posttreatment alterations be distinguished from recurrences?].

The recognition of recurrent soft tissue sarcomas and the differentiation from post-treatment alterations is complex. This article aims to assist the clinical radiologist in the systematic evaluation of local follow-up imaging in soft tissue sarcoma patients. Soft tissue sarcomas encompass multiple entities with different recurrence rates and follow-up intervals. Approved and up to date recommendations are provided, including imaging techniques. The past medical history of the patient, the clinical situation and previous therapies should be known in detail, including surgery, radiation therapy and chemotherapy. Previous imaging results should be consulted, if available. This article describes the time-dependent imaging spectrum of local post-therapeutic as well as local treatment-related complications. These include early complications, such as seromas, hematomas and infections, as well as late complications, including edema, fibrosis and joint stiffness, and also inflammatory pseudotumors, which may occur after variable time intervals. The imaging appearance of local recurrent and radiation-associated sarcoma are elucidated. In particular, magnetic resonance imaging (MRI) criteria are provided, which may help in differentiating post-therapeutic alterations from recurrent soft tissue sarcomas.