Vulvar seborrheic keratosis: is there a relationship to human papillomavirus?

We sought to determine the prevalence of human papillomavirus (HPV) subtypes in vulvar seborrheic keratoses (SK) by polymerase chain reaction (PCR) in women with a theoretically low risk of recent HPV transmission. We also attempted to identify which histopathologic features best correlated with HPV and specific subtypes.

Twenty-eight cases of vulvar SK in women older than 50 years old were retrospectively pulled from our files from a 7-year period. Cases were histologically examined for the presence of 7 features: parakeratosis, horn cysts, pigmentation, "clonal" cells, papillomatosis, "whorls," and reticulation of rete. For controls, PCR was performed on all cases for HPV detection and typing. Ten cutaneous SK and 7 vulvar condyloma acuminata were also evaluated for HPV by PCR.

Twenty-one vulvar SK had sufficient genetic material for HPV PCR analysis. Only 3 (14.29%) were positive for HPV, 2 were type 6, and 1 was an unknown type. All cutaneous SK were negative and all condyloma acuminatum were positive for HPV. There was no histologic feature that separated HPV-positive from HPV-negative vulvar SK, although there was a tendency for parakeratosis to be associated with HPV positivity.

The rate of HPV positivity in vulvar SK in women older than 50 years is much lower than expected and not statistically significantly associated with specific histologic features. One explanation may be that vulvar SK have diminishing levels of HPV genetic material in the relatively older ages of the patients in our study. Alternatively, vulvar SK may have no relationship to HPV, and strict histologic criteria may separate vulvar SK from condyloma acuminatum. In this instance, the few cases of HPV-positive vulvar SK may reflect incidental persistence of HPV in vulvar epidermis. Furthermore, these possibilities may vary among different populations, for example, based on patient age.