A Case Report on Recurrent Merkel Cell Carcinoma with Metastasis to Colon Treated with Pembrolizumab

Merkel Cell Carcinoma (MCC) is a cutaneous neuroendocrine cancer with a poor prognosis. It is characterized by a high rate of recurrence and metastases to regional as well as distant sites. Clinically, MCC often manifests as a single painless, hard nodule in the sun-exposed area. The diameter is often <2cm, but in few cases, it can be >2cm, with rapid growth and metastases to lymph nodes. MCC carcinoma is diagnosed in the advanced stage because of its resemblance with other skin cancers. Because of the aggressive nature of this cancer, the overall prognosis is found to be poor. In this case report, we report a 71-year-old gentle male who presented with a painless mass in the right axilla three years ago, was diagnosed with MCC of the skin and was treated with surgical removal of the mass together with radiation therapy. Two years later, the follow-up visit restaging PET CT scan was done and was found to have a new intense uptake in the soft tissue nodule adjacent to the proximal sigmoid colon. Biopsy confirmed the metastasis of MCC to the colon. We are reporting an uncommon location of MCC metastasis to the intestine for which he got treated with immunotherapy.