The Clinicopathologic Challenge of Nonneoplastic Vulvar Acanthosis

The aim of the study was to evaluate clinicopathologic features of cases demonstrating an acanthotic tissue reaction not clearly consistent with psoriasis, lichen simplex chronicus, mycosis, or condyloma.

This is a retrospective pathologic case series of biopsies reported as "benign acanthotic lesion" and "acanthotic tissue reaction" that lacked a clear diagnosis on expert review. Cases with nuclear atypia were excluded. Clinical and histopathologic data were collected, immunohistochemistry for p16 and p53 were obtained, and molecular testing for 28 common anogenital human papillomavirus (HPV) genotypes was undertaken.

There were 17 cases with a median age of 47 years. Unilaterality and medial location were clinical reasons for diagnostic difficulty. Histopathologic uncertainty often related to lack of papillary dermal fibrosis to support lichen simplex chronicus or psoriasiform lesions without parakeratosis, subcorneal pustules, and/or mycotic elements. Firm pathologic diagnoses were not possible, but 3 groups emerged: favoring chronic dermatitis, favoring psoriasis, and unusual morphologies. p16 results were negative or nonblock positive while p53 was normal or basal overexpressed. Human papillomavirus testing was negative in 12, low positive for HPV 16 in 1, unassessable in 3, and not requested in 1.

There is a group of acanthotic tissue reactions that cannot be classified with standard histopathologic assessment. Further clinicopathologic research into unilateral acanthotic lesions may provide insight into separation of psoriasis and mycosis when organisms are absent. Once nuclear atypia is excluded, immunohistochemistry for p16 and p53 and HPV molecular testing do not assist in diagnostic identification.