Biopsy of a persistent exophytic area on the vulva of a 60 year old woman demonstrates a squamous epithelial lesion. No koilocytes are seen. The lesions show papillary projections composed of disordered, squamous epithelium with well differentiated cells. The basement membrane at the dermal-epidermal junction is focally disrupted by squamous cell groups extending deep into the dermis. Which of the following diagnoses is most accurate?

The disruption of the basement membrane with cell groups extending deep into the dermis indicates that this is invasive squamous cell carcinoma of the vulva, which may arise in vulvar intraepithelial neoplasia, in condyloma, or spontaneously. The latter type (which is likely here) tends to be well differentiated, while the former two are often poorly differentiated. Condyloma acuminatum would contain koilocytes and would not cross the basement membrane. Extramammary Paget's disease would probably contain individual tumor cells that stain for mucin. The lesion of vulvar intraepithelial neoplasia does not cross the basement membrane. Ref: Karam A. (2013). Chapter 47. Premalignant & Malignant Disorders of the Vulva & Vagina. In A.H. DeCherney, L. Nathan, N. Laufer, A.S. Roman (Eds),CURRENT Diagnosis & Treatment: Obstetrics & Gynecology, 11e.