Vulvar Merkel cell tumor with glandular and squamous differentiation.

A case of a Merkel cell tumor of the vulva is presented. In addition to the typical microscopic, immunohistochemical, and ultrastructural features of Merkel cell tumor, there were areas of squamous and glandular differentiation. This is the ninth reported case of a vulvar Merkel cell tumor, and the first where squamous and glandular differentiation were seen. The findings support an origin of Merkel cell tumors from pluripotential stem cells.