Early squamous cell carcinomas of penis and vulva, the so-called precancerous lesions of genital region, have similarities in morphology and pathogenesis, but they also have, unfortunately, similarities in their classification and nomenclature that are quite confusing. Archaic terminologies lacking epidemiologic value and good reproducibility are still in use and, armed with their historical importance, compete for space in medical publications against modern terms which were coined on solid scientific basis.

With this in mind, I've decided leave behind terms such as Bowen's disease, erythroplasia of Queyrat, and so forth, in order to revere the efforts of the International Society for the Study of Vulvar Disease in developing a simplified two-tier classification for vulvar intraepithelial neoplasia and the efforts of Dr. Antonio L. Cubilla et cols. in adapting this classification into penile intraepithelial neoplasia. Now, every time I report an early squamous cell carcinoma of penis or vulva, I feel free to repeat the famous Newtonian phrase: "I have seen further it is by standing on ye shoulders of giants!"

The simplified two-tier classification for penile intraepithelial neoplasia and vulvar intraepithelial neoplasia are easy to learn and have excellent reproducibility. Moreover, clinicopathologic correlation is readily achieved in both.

Penile and vulvar intraepithelial neoplasia are classified in differentiated variant and undifferentiated variant. Typically, the former is not associated to HPV infection, but tends to occur in older patients in the setting of lichen sclerosus or other chronic scarring dermatitis. The latter is related to a HPV-induced precursor and tends to affect younger patients, many of them immunocompromised ones.

Microscopic features are also distinctive. Differentiated genital intraepithelial neoplasia shows a thickened epidermis with abnormal maturation, but relatively preserved polarity, characterized by enlarged hypercromatic nuclei in the basal layer and ample eosinophilic cytoplasm in the spinous layer. Undifferentiated genital intraepithelial neoplasia of basaloid-type is flat and displays immature cells replacing the whole thickness of the epidermis, and the wart-type is papillomatous and exhibit marked cellular pleomorphism and prominent koilocytic changes.