A 67-year-old woman was treated with neoadjuvant chemotherapy, esophagectomy, and subsequent radiotherapy for T3N1 poorly differentiated adenocarcinoma of the esophagus. Five months after surgery, a routine follow-up CT demonstrated a 1.2-cm soft tissue mass in the posterior mediastinum suspicious for local recurrence. An FDG-PET/CT study confirmed tumor in the posterior mediastinum and also showed focal areas of increased tracer uptake within several muscles. Skeletal muscle is one of the most unusual sites of metastatic disease, although it is probable that the more frequent use of FDG-PET imaging will lead to an increase in the detection of such lesions.