A Rare Presentation of Colorectal Cancer with Unusual Progressive Intramuscular and Subcutaneous Metastatic Spread.

Colorectal carcinoma is one of the most common causes of cancer-related death, worldwide. Recently, due to the introduction of novel imaging and therapeutic techniques, five-year survival of patients has increased. However, distant metastasis is still expected in half of the patients. Colorectal cancer tends to target the abdominal cavity, liver, lungs, and bones as the common sites of metastasis. Nevertheless, rare cases of muscle metastasis have been reported. This report presents a 23-year-old male, who despite chemotherapy, demonstrated gradual progressive disease and metastases to the submandibular region, lungs, adrenal gland as well as muscles and subcutaneous tissues. He had developed multiple asymptomatic muscular metastases metachronously over two-year time period discovered on an 18 FDG-PET/CT, namely in the deltoid, external oblique abdominis, rectus abdominis, and quadriceps muscles, as well as one of the extrinsic muscles of the tongue. The presence of distant, especially extrahepatic metastasis, adversely affects the prognosis of colon carcinoma. Since limited cases of muscle metastasis have been reported in carcinoma of colon, the underlying pathophysiology, optimum treatment, and prognostic issues are yet to be substantiated.