Purely epithelioid malignant peripheral nerve sheath tumor of the vulva.

Primary malignant peripheral nerve sheath tumors(MPNST) of the vulva are extremely rare and most of them are composed of a spindle cell component. A few cases of MPNST containing partially or purely epithelioid cells have been reported. Purely epithelioid MPNST differ from the ordinary epithelioid MPNST due to the absence of a spindle cell component. We present the first case of purely epithelioid MPNST arising in the vulva reviewing in the world literature without definite evidence of von Recklinghausen's disease or nerve involvement. The patient was a 63-year-old woman with a palpable vulvar mass, 6 x 4 x 1.5 cm in dimension, was not encapsulated but well-demarcated, ovoid and rubbery and showed pale yellow, homogeneous, fish-flesh appearance with focal cystic changes on cut surface. The histologic features consisted of solely epithelioid cells which were arranged in tight clusters or cords with solid growing pattern and focally scattered rosette-like structures. According to the immunohistochemical results, most of tumor cells were strongly positive for neuron specific enolase, and some of them were weakly positive for S-100 protein and vimentin. We considered that purely epithelioid MPNST would represent a certain degree of differentiation toward nerve or neuronal cells rather than Schwann cells.