Ossifying skeletal muscle metastasis as an initial manifestation of colorectal adenocarcinoma

Skeletal muscle metastases from colorectal cancer (CRC) are very rare. They have usually been described in patients with known CRC and as a well-defined mass. In this case report, we present a unique case of diffuse and ossifying skeletal muscle metastasis as the first manifestation of CRC. A 36-year-old man presented with progressive left thigh swelling and left hip pain of 6 months duration. He denied any gastrointestinal complaints. CT and MRI of the thigh showed diffuse muscular swelling, signal abnormalities with linear calcifications involving the muscles of the posterior and medial compartments of the left thigh and both gluteal regions. Histology confirmed the metastatic nature of a colorectal adenocarcinoma. The patient was treated with chemotherapy and showed a good evolution after 6 months of follow-up.