Normal Vulvar Histology: Variation by Site

Objective The aim of the study was to assess the histology of normal vulvar skin with attention to anatomic location and epithelium type. Materials and Methods We performed a retrospective histologic review of 118 vulvar biopsies and excisions obtained between 2010 and 2014 with adjacent normal skin or mucosa. Exclusions included age younger than 18 years, vestibulectomy, labiaplasty, inflammatory dermatoses, and insufficient normal tissue for assessment. Stratum corneum morphology was assessed as basket weave, compact, or intermediate. Stratum granulosum cell layer number and epithelial thickness were recorded. Dermal lymphocytic infiltrate was described as nil, sparse, moderate, or dense. Fischer exact test, Pearson (2), and Student t test were used for statistical analysis. Results There were 7 cases from mons pubis, 11 from perineum, 83 from labia, and 17 from vestibule. In the skin, the stratum corneum morphology was basket weave in 31%, compact in 35%, and intermediate in 34%. Stratum corneum at the mons pubis was uniformly basket weave, whereas at perineum, it was either compact or intermediate (7/7 vs 0/11; p < .001); the labia demonstrated all 3 morphologies. Parakeratosis (PK) was identified at the specimen edge in 4 cases of hairless skin and 7 cases of squamous mucosa. Mean epithelial thickness and dermal lymphocytic infiltration were similar in specimens with and without PK. Conclusions Compact stratum corneum of vulvar skin and a zone of PK at the mucocutaneous junction may be normal histological findings. Pathologists need to be aware of site-related differences of the vulvar epithelium to avoid overdiagnosis of pathological conditions.