A case of a Merkel cell tumor of the vulva is presented, In addition t
o the typical microscopic, immunohistochemical, and ultrastructural fe
atures of Merkel cell tumor, there were areas of squamous and glandula
r 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. (C) 1996 Academic Press, Inc.