Clinicopathologic comparison of vulvar and extragenital lichen sclerosus: histologic variants, evolving lesions, and etiology of 141 cases.

Lichen sclerosus (LS) is a persistent inflammatory dermatosis of unknown etiology with a predilection for the vulva, where it is a risk factor for carcinoma. We performed a clinicopathologic study on 121 cases of vulvar LS and 20 of extragenital LS, and we reviewed 49 vulvectomy specimens with LS to define morphologic findings, identify the earliest lesions, and correlate outcomes with histologic findings. The vulvar LS lesions were pruritic/burning, white/red, ill-defined patches predominately affecting the labia, perineum, introitus, and perianal region. The extragenital LS lesions were asymptomatic, pink to ivory white, coalescing macules or patches with well-defined borders. All of the LS cases showed dermal sclerosis, vacuolar interface changes, and a lymphocytic infiltrate underlying the sclerosis, but vulvar LS showed changes of lichen simplex chronicus or spongiotic dermatitis, dermal eosinophils, and a frequent absence of atrophy. The presence of eosinophilic spongiosis, marked lymphocyte exocytosis, dermal eosinophils, and excoriations predicted poor symptomatic response to treatment. Patch testing is recommended for these individuals as these findings suggest an allergic contact dermatitis. Examination of vulvectomy specimens revealed either a lichenoid interface or a spongiotic dermatitis in continuity with pathognomonic LS. Additionally, in these contiguous regions, we identified histologic changes that might represent evolving lesions of LS, suggesting a multifactorial etiology. In conclusion, vulvar LS was significantly different clinicopathologically from extragenital LS, and if only classic features of LS were used for pathologic diagnosis, many cases of vulvar LS would be missed. Therefore, we proposed as the minimal histologic criterion for LS the presence of a vacuolar interface reaction pattern in conjunction with dermal sclerosis (homogenized and hyalinized eosinophilic collagen bundles) of any thickness intervening between the inflammatory infiltrate and epithelium and or vessel walls.