Subcutaneous and Muscle Metastases From Rectal Adenocarcinoma on 18F-FDG PET/CT Imaging.

A 50-year-old man with T4 N2 M1 poorly differentiated adenocarcinoma of the rectum underwent neoadjuvant chemotherapy, surgical resection, and subsequent chemotherapy. Six months after surgery, routine follow-up CT revealed the presence of abdominal wall subcutaneous nodules associated with bilateral pulmonary and renal nodules, indicating metastases. Further 18F-FDG PET/CT scan revealed a high number of subcutaneous and muscle metastases. Metastasis of rectal adenocarcinoma to subcutaneous tissue or skeletal muscle is considered rare.