Differentiated vulvar intraepithelial neoplasia (d-VIN) is an HPV-independent precursor to vulvar squamous cell carcinoma. The histology of d-VIN lesions is difficult to differentiate from that of non-neoplastic epithelial disorders, especially lichen sclerosus (LS). The authors present a case of LS, where relying on histopathology alone could have led to misdiagnosis. The patient was a 17-year-old female patient with clinical features of vulvar dermatitis and LS for 2 years. She was counseled to apply clobetasol 0.05% to the affected area daily but reported no improvement after 6 months. A biopsy of the right labia majora revealed histologic findings typical of d-VIN and near-contiguous p53 expression. These features are characteristic of d-VIN. However, d-VIN is exceedingly rare in young patients. The case was reviewed by 6 dermatopathologists and gynecologic pathologists, who observed that the degree of inflammation would be unusual postclobetasol therapy and could be due to noncompliance. A review of the patient's chart revealed that she "does not always remember to apply" clobetasol. The patient's clinician confirmed that there were compliance issues, and the follow-up biopsy was negative for d-VIN. The case was signed out as LS, with a note describing the above, and to rebiopsy if concern persisted. The authors conjecture that inflammatory infiltrates in the biopsied area caused reactive atypia due to lack of adherence to treatment. Although the patient's age helped rule out d-VIN, similar cases in elderly patients may be occurring. Pathologists must be aware that reactive forms of untreated LS can mimic d-VIN, to avoid misdiagnosis.
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