Vulvar intraepithelial neoplasia and skin appendage involvement.

Vulvar intraepithelial neoplasia may extend into the pilosebaceous units of the hairy and non-hairy skin of the vulva, and inadequate removal may cause treatment failure. We measured with a calibrated microscope the thickness of vulvar intraepithelial neoplasia and the depth to which it extended into the underlying pilosebaceous units of the vulvar skin. The mean thickness of vulvar intraepithelial neoplasia in 329 histologic sections from 62 cases was 0.38 mm; 99.5% of all vulvar intraepithelial neoplasia measured less than 0.77 and 0.69 mm in the hairy and non-hairy skin, respectively. Sebaceous-gland and hair-follicle involvement by vulvar intraepithelial neoplasia was 21 and 32%, respectively. The mean depth of sebaceous-gland involvement was 0.77 mm in the hairy skin and 0.50 mm in its non-hairy counterpart; 99.5% of all vulvar intraepithelial neoplasias extended less than 2.03 and 1.07 mm in the hairy and non-hairy skin, respectively. The mean depth of hair-follicle involvement was 1.04 mm; 99.5% of all hair follicles were involved less than 2.55 mm. Our findings suggest that removal of vulvar intraepithelial neoplasia to a depth of 1.0 and 2.0 mm in the non-hairy and hairy skin, respectively, is appropriate for successful treatment.