Plasmacytoid squamous cell carcinoma of the vulva.

Although neoplastic cells with a plasmacytoid appearance have been reported in a variety of tumors, to the best of our knowledge, a plasmacytoid squamous cell carcinoma (SCC) of the vulva or skin has heretofore not been described. We document the case of a 92-year-old female patient with a history of multiple excisions for vulvar verrucous and SCCs, who presented with a 3-cm, symptomatic, polypoid mass of the left upper vulva. Histologically, sheets of dyscohesive relatively monotonous plasmacytoid and spindle cells were found dispersed throughout the dermis. The neoplastic cells expressed cytokeratins AE3, 5/6, and 903, p63, and the plasma cell markers CD138 (syndecan-1) and VS38. The neoplastic cells did not label with S-100 protein, Melan-A, smooth muscle actin, desmin, Kappa and Lambda light chains, epithelial membrane antigen, MOC-31, uroplakin III, thrombomodulin, and E-cadherin. Based on the tumor location, morphology, and immunohistochemical results, the diagnosis of plasmacytoid SCC of the vulva was rendered. Six months after complete excision, she developed regional inguinal lymph node and pulmonary metastases and died. Like other plasmacytoid malignancies, vulvar plasmacytoid SCC is a rare and likely aggressive variant of SCC, which can pose significant diagnostic challenges. Squamous cell carcinoma should also be considered in the differential diagnosis of neoplasms with plasmacytoid cytology. To correctly classify plasmacytoid malignancies, a wide panel of immunohistochemical markers must be used.