Angiosarcoma is a rare malignant neoplasm, accounting for 1-2% of all sarcomas. The main cause of developing secondary angiosarcoma is radiotherapy. We analysed the case of a 52-year-old woman with breast cancer, who had undergone breast-conserving therapy. Four years after finishing treatment, she was diagnosed with secondary angiosarcoma in the irradiated area. The patient underwent a mastectomy. The disease relapsed six months after the operation in form of local recurrence, as well as liver and lung metastases. The patient's condition gradually deteriorated despite treatment (chemotherapy and symptomatic management). The patient died due to cardiorespiratory failure nine months after the diagnosis of secondary malignancy.

Recently, we have gained access to innovative radiological and metabolic examination methods. One of these methods is PET/MRI with fluorodeoxyglucose (18F-FDG) tracer. Performing this innovative examination in a 69-year-old woman with diagnosed rectal cancer brought additional benefits. The use of PET/MRI resulted in precise clinical staging, the detection of a synchronous early-stage right breast cancer, and in the optimisation of treatment of both cancers. To date, diagnostic guidelines concerning rectal and breast cancers do not recommend the use of functional imaging for routine imaging.