A Case Report of Leptomeningeal Carcinomatosis Secondary to Recurrent Merkel Cell Carcinoma after Avelumab

Abstract

Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine cancer with a high mortality rate of 33% to 46%. Merkel cell is a type of epidermis cell receptor responsible for contact sensitivity and is known to have neuroendocrine properties. Treatment of Merkel cell carcinoma with avelumab has been prominsing, but its rarity and poor prognosis necessitates close follow up. A 71-year-old woman presented with a left forearm mass that was initially suspected to be a sebaceous cyst. After surgical excision and biopsy, she was diagnosed with Merkel cell carcinoma. The patient underwent avelumab treatment for 2 years, with remission of cancer for 24 months. A positron emission tomographic scan at 24 months of treatment noted uptake in the left axilla and portocaval regions. Despite receiving different combinations of immunotherapy, chemotherapy, and radiation, the patient's cancer metastasized to the leptomeninges. She was transitioned to hospice and passed away 3 months after diagnosis of leptomeningeal carcinoma. This case highlights the efficacy of avelumab in keeping patients in remission, which can offer increased quality of life. However, it also highlights the aggressive nature of Merkel cell carcinoma and the importance of surveillance for early detection of recurrence.