Anatomic Pathology: Gynecologic Pathology

534) The histologic finding of this vulvar lesion is MOST compatible with:

• VIN III encompasses the older terms severe dysplasia and carcinoma in situ and is defined as involvement of greater than two thirds of the epithelium by dysplastic cells.

• Human papillomavirus (HPV) DNA is identified in numerous cases of warty and basaloid VIN. However, HPV DNA is distinctly absent in differentiated VIN.

• The warty pattern of VIN is characterized histologically by a spiked appearance that looks like warts. There is striking cellular pleomorphism. Koilocytes are prominent. Multinucleate cells, corps ronds, and dyskeratotic cells all are common. By contrast, the basaloid pattern of VIN has a flat surface on histologic sections. The entire lesion is composed of small undifferentiated cells that resemble the normal basal cell. Koilocytes are much less common. In some patients, a mix of these two histologic patterns may be present.

• Differentiated VIN is rare, accounting for only 2% to 10% of cases of VIN. This pattern is often missed because of its deceptive histology. Histologic sections reveal an absence of pleomorphism, cellular disarray, and diffuse nuclear atypia. Cellular differentiation is increased. The lesion is often misdiagnosed as squamous hyperplasia or acanthosis. The cytoplasm is characteristically eosinophilic.

• In the lower two thirds of warty and basaloid VIN, p16 staining is positive, and it is almost always negative in differentiated VIN. In contrast, p53 staining is positive in a high percentage of differentiated VIN, whereas far fewer cases of basaloid and warty VIN demonstrate p53 staining.

Hart WR: Vulvar intraepithelial neoplasia: historical aspects and current status. Int J Gynecol Pathol 2001;20(1):16-30.

Santos M, Montagut C, Mellado B, et al: Immunohistochemical staining for p16 and p53 in premalignant and malignant epithelial lesions of the vulva. Int J Gynecol Pathol 2004;23(3):206-214.

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