While the liver and lung are primary targets for distant metastasis from colorectal carcinoma, metastasis in other distant sites is rarely found. We report herein an unusual case of metastasis to the skeletal muscle of the right forearm from an adenocarcinoma of the transverse colon. A 60-year-old man was originally admitted to our hospital for surgical treatment of an intestinal obstruction caused by a transverse colon carcinoma. Transverse colon resection along with lymph node dissection was performed and no evidence of distant metastatic foci was found. Angiography-enhanced computed tomography scanning done 14 months after the first operation revealed multiple hepatic metastases which were resected. A metastasis was subsequently detected in the right extensor carpi ulnaris muscle 2 years after the primary resection, and a major part of the right extensor carpi ulnaris and the extensor digiti minimi muscle were resected, warranting a sufficient margin of 5 cm of normal tissue from the tumor. Reattachment of the residual muscles into the ulna was performed. Metastases to bone and/or soft tissues from colorectal carcinomas are extremely rare and to our knowledge, only eight other cases have been reported in the world literature. This low incidence may be related to the anatomical characteristics and/or the biochemical environment of the skeletal muscle, but it is also possible that the true incidence is underestimated. Recent improvements in interventional radiological procedures may facilitate a diagnosis of skeletal muscle metastasis being made more frequently.
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