Long-term complete response in a breast cancer patient with skeletal muscle metastases diagnosed using 18F-FDG-PET

Common sites for metastatic spreading from breast cancer are bones, lungs and liver, the skeletal muscle being an unusual site. Although rare, when skeletal muscle metastases occur they are associated with a poor prognosis. These metastases are clinically difficult to diagnose since they can be found without pain symptoms. Radiologically, magnetic resonance imaging has been considered better than computed tomography for imaging of the muscles and has been the first procedure to use in case of muscle metastasis suspicion. In the last years, positron emission tomography (PET) with 18Fluorine-2-fluoro-2-deoxy-d-glucose (18F-FDG) has emerged as the main imaging tool. We here report a case of a hormone receptor-positive/human epidermal growth factor receptor 2-negative patient who presented with a recurrent infiltrating ductal carcinoma and diffuse skeletal muscle metastases detected by 18F-FDG-PET. The treatment of the patient with exemestane and everolimus led to a durable complete response.