HPV-associated Vulvar Trichoblastoma: A Diagnostic Pitfall

Area of Science:

• Dermatopathology
• Gynecologic Oncology

Background:

• Vulvar trichoblastoma is a rare benign adnexal neoplasm.
• High-grade vulvar intraepithelial neoplasia (VIN3) is a premalignant lesion associated with HPV.
• Synchronous occurrence of these entities is exceptionally rare.

Purpose of the Study:

• To report a rare case of synchronous vulvar trichoblastoma and VIN3.
• To highlight the diagnostic challenges posed by overlapping features.
• To emphasize the importance of accurate differentiation from invasive squamous cell carcinoma.

Main Methods:

• Histopathological examination of a vulvar tumor.
• Immunohistochemical staining for p16.
• RNA in situ hybridization for high-risk HPV detection.

Main Results:

• A 35-year-old woman presented with a deep dermal tumor and superficial VIN3.
• The trichoblastoma exhibited basaloid nests with folliculo-sebaceous differentiation and increased mitoses.
• Both lesions showed diffuse p16 positivity and high-risk HPV detection, creating a diagnostic pitfall.

Conclusions:

• The morphologic and immunophenotypic overlap between vulvar trichoblastoma and VIN3 can mimic invasive squamous cell carcinoma.
• Careful histological assessment and a panel of immunohistochemical markers are crucial for accurate diagnosis.
• Distinguishing trichoblastoma from invasive carcinoma is essential to prevent overtreatment.