Merkel cell carcinoma of the skin with leptomeningeal metastases.

Merkel cell carcinoma is a rare skin tumor that is thought to arise from epithelial cells that have undergone neuroendocrine differentiation. It usually presents in older adults and has a slight male predominance. The most frequent site of occurrence is in the head and neck. It is an aggressive disease that has a high rate of local-regional and distant recurrence. Optimal treatment is controversial but generally consists of surgery and adjuvant radiotherapy. The role of chemotherapy is less defined. This report documents the first known case of Merkel cell carcinoma with perineural spread to the central nervous system with leptomeningeal dissemination. Whether this represents a more aggressive variant is unknown. Regardless, this pattern of spread is likely a rare event.