Malignant primary melanoma of the colon: a case report.

Melanoma is most associated with cancer of the skin. However, a small subset of these melanomas can be a primary malignancy of other mucosal membranes. A 55-year-old male presented to the gastroenterologist with 1 year of symptoms typical of colon cancer including bloating, abdominal pain and weight loss. He underwent colonoscopy and a mass was seen in the transverse colon that was later proven melanoma. A PET CT scan showed this was his only focus of disease. He then underwent a laparoscopic-assisted extended right hemicolectomy. He had an uneventful postoperative course. He was thoroughly examined for other sources of melanoma such as cutaneous, anal and uveal sources. He has recovered well at home and is receiving adjuvant pembrolizumab immunotherapy. Mucosal primary melanomas have a worse 5-year survival than primary cutaneous melanomas. A multi-disciplinary approach is necessary to treat and properly diagnose these malignancies.