A late-presenting deltoid metastasis in a male in his 30s with an adenocarcinoma of the colon, a case report

Introduction: Adenocarcinoma of the colon is the 4th most common malignancy globally with an age-standardized incidence rate of 6.1/100.000 males in South-Central Asia. The most common sites of metastasis for colorectal adenocarcinoma are the liver, lung, peritoneum and bone via lymphatic, hematogenous or direct spread. Metastases to skeletal muscles are rare and estimated to constitute less than 1% of all metastases. We present a case of a delayed adenocarcinoma of the colon metastasis in the left deltoid muscle. Case presentation: A man in his 30s, presented at our hospital with right lower quadrant abdominal pain, and weight loss. Biopsy showed a poorly-differentiated mucin-secreting adenocarcinoma which was treated with chemotherapy and a hemicolectomy. Seven years later, he presented with complaints of left shoulder pain and swelling. Biopsy of the deltoid muscle showed a pathology report consistent with the previous malignancy in the caecum; metastatic poorly-differentiated adenocarcinoma. A surgical wide marginal excision of the lesion with therapeutic intent was performed. Conclusion: Metastases to skeletal muscles are rare and their detection and timely treatment depend highly on provider’s index of suspicion. The presence of a painful muscle mass in a patient with a prior history of a carcinoma must be evaluated carefully for possible metastases even if common sites are clear.