Anogenital Intraepithelial Neoplasia and Cancer

Pathogenesis, Viral Integration and How the Epithelium Progresses

Viral Genome Integration and Loss of the E2 Regulator

• In benign lesions the virus persists as a circular episome, but in HSIL, HR-HPV (especially HPV 16) tends to integrate its DNA into the host cell's genome.
• Integration disrupts the viral E2 gene. Because E2 normally keeps the E6/E7 promoter in check, losing it unleashes uncontrolled overproduction of the E6 and E7 oncoproteins.

E6/E7 Oncoprotein Effects and p16INK4a Block Positivity

• E6 and p53 degradation: E6 binds the ubiquitin ligase E6AP and drives p53 to be broken down by the proteasome. The keratinocyte loses its ability to repair DNA and to trigger programmed cell death (apoptosis).
• E7 and pRb inactivation: E7 binds tightly to pRb, releasing the transcription factor E2F and pushing the cell relentlessly into the S phase of the cell cycle.
• p16INK4a accumulation (the p16 biomarker): Loss of pRb function removes the negative feedback loop, so the cell produces large amounts of p16INK4a. Diffuse immunostaining through the full thickness of the epithelium (block positivity) is biological confirmation of HR-HPV-driven HSIL.

Clinical Features and Classification of AIN, VIN, PIN and VaIN

Vulvar Intraepithelial Neoplasia (VIN):

• Classic/usual VIN (HPV-associated HSIL): Usually seen in younger women, often multifocal and closely linked to HPV 16/18. It appears as white (hyperkeratotic), dark red or gray-black papules or plaques with a rough surface, causing persistent itching and burning.
• Differentiated VIN (dVIN, HPV-independent): Not related to HPV; it develops on long-standing lichen sclerosus in older women. Although it makes up only about 10% of cases, dVIN progresses to invasive cancer faster and more aggressively than classic VIN.

Anal and Penile Intraepithelial Neoplasia (AIN and PIN):

• Anal intraepithelial neoplasia (AIN): Common in men who have sex with men (MSM) and people living with HIV. It is usually silent and detected only on high-resolution anoscopy (HRA), as opaque acetowhite patches or looped blood vessels in the anal canal.
• Penile intraepithelial neoplasia (PIN): Includes Bowen disease, bowenoid papulosis and erythroplasia of Queyrat. It presents as coalescing gray-brown papules or fragile, velvety red plaques on the foreskin or shaft of the penis.

Invasive Anogenital Squamous Cell Carcinoma (SCC):

• Develops when abnormal cells break through the basement membrane and invade the underlying dermis or stroma.
• Clinically: a cauliflower-like growth or an ulcer with a firm base and raised edge that bleeds easily, produces foul-smelling discharge and can be very painful.

Our Diagnostic Process at Haute-Derma

High-Resolution Examination (HRA / Colposcopy / Mucoscopy) With Acetic Acid: We apply 5% acetic acid and look for an acetowhite reaction (opaque whitening). Magnified examination of the blood-vessel pattern then looks for punctation and mosaicism, two warning signs of HSIL/high-grade AGIN.

Targeted Biopsy and Immunohistochemistry (IHC):

• Punch biopsy, guided by HRA, from the area with the most abnormal vessels.
• p16INK4a and Ki-67 dual staining: distinguishes LSIL (p16 negative or basal-only, Ki-67 limited to the lower third of the epithelium) from HSIL (diffuse p16, Ki-67 extending into the upper two-thirds).

HPV Genotyping (Real-Time PCR) and Liquid-Based Cytology: Anal, cervical or vaginal smears (Pap/liquid-based cytology) are combined with real-time PCR HPV genotyping to measure viral load and track the risk of progression.

Management, Treatment and Cosmetic Preservation at Haute-Derma

Topical Medical and Immunomodulating Therapy (For Extensive HSIL)

• Imiquimod 5% cream: A 12–16-week course. By stimulating innate immunity through TLR-7, it creates a local inflammatory response that clears HR-HPV-infected cells. It is a first-choice option for multifocal VIN 2/3 and AIN 2/3 in younger patients who want to preserve tissue.
• 5-fluorouracil (5-FU 5%): An antimetabolite that blocks DNA replication in abnormal cells, used for scattered VaIN or AIN lesions.

Tissue-Sparing Device-Based Treatments

• Superpulsed CO2 laser microablation (ablative laser therapy): The 10,600 nm wavelength precisely removes the full thickness of the abnormal epithelium (controlled depth of 1–2 mm) while leaving the underlying dermis intact. This keeps the risk of adhesions, anal narrowing or contracting vulvar scars as low as possible.
• Photodynamic therapy (5-ALA PDT): A 5-ALA photosensitizer is applied and then activated with red light (630 nm). It selectively destroys HSIL cells without harming the surrounding healthy tissue.

Surgical Excision and Adjuvant Vaccination

• Wide local excision / Mohs surgery: Required when biopsy shows invasive SCC or dVIN (HPV-independent VIN).
• Adjuvant Gardasil 9 vaccination: The vaccine does not cure existing lesions, but giving Gardasil 9 to patients with AGIN boosts systemic antibody responses and may help lower the risk of new lesions recurring after the original precancer has been removed.