Posted in

Managing Vulvar Precancer: Key Updates for Physicians

•Posted inObstetrics and Gynaecology

Vulvar cancer rates are currently increasing, requiring heightened awareness from clinicians. Therefore, understanding the key premalignant precursors remains vital. These precursors include high-grade squamous intraepithelial lesions (HSIL) and differentiated vulvar intraepithelial neoplasia (dVIN), collectively known as Vulvar intraepithelial neoplasia. Recent changes in classification, along with a deeper understanding of the distinct causes—specifically human papillomavirus (HPV)-associated and HPV-independent pathways—have greatly influenced diagnosis and effective patient management. Furthermore, this review summarizes the evolving terminology and outlines the critical need to distinguish between the two major subtypes to ensure appropriate care is delivered.

Evolving Terminology for Vulvar Precancer

The International Society for the Study of Vulvovaginal Disease (ISSVD) led the charge in updating the nomenclature. Formerly, doctors used terms like VIN 1, VIN 2, and VIN 3. Consequently, the current system simplifies the classification into three main categories. First, low-grade vulvar squamous intraepithelial lesion (LSIL) describes condyloma or an HPV effect, and it is usually not considered a true precancer. However, the clinically significant precancers are vulvar HSIL (High-Grade Squamous Intraepithelial Lesion) and differentiated VIN (dVIN). HSIL corresponds to the older “usual type VIN.” Meanwhile, dVIN represents the non-HPV-associated subtype. Correctly identifying these specific subtypes is paramount for guiding treatment decisions.

Distinguishing HPV-Associated Vulvar Intraepithelial Neoplasia (HSIL)

HPV-associated Vulvar intraepithelial neoplasia, or HSIL, is the most common subtype, accounting for over 80% of cases. It primarily affects younger women, typically in their 40s. High-risk HPV types, especially HPV 16, cause this lesion. Smoking and immunosuppression, such as HIV, are established risk factors that increase the likelihood of developing HSIL. Clinically, HSIL lesions are often multifocal. Furthermore, treatment options for HSIL are more varied. Specifically, doctors can choose wide local excision, laser ablation, or topical immune-modulator therapy like Imiquimod. Although HSIL carries a risk of progression to cancer, dVIN has a much higher malignant potential.

Differentiated Vulvar Intraepithelial Neoplasia (dVIN): The HPV-Independent Pathway

Differentiated VIN (dVIN) is less common, making up only about 5% of VIN diagnoses. Unlike HSIL, dVIN develops independently of HPV infection. This subtype typically occurs in older, post-menopausal women, often around 60 to 80 years old. Consequently, dVIN is strongly associated with chronic inflammatory vulvar dermatoses, notably lichen sclerosus. Experts consider dVIN the real precursor lesion to vulvar squamous carcinoma because it has a significantly higher progression rate to invasive cancer—up to 85% if left untreated. Therefore, the treatment of choice for dVIN is aggressive wide local surgical excision. Unlike HSIL, topical treatments are generally ineffective for this highly aggressive subtype.

Frequently Asked Questions

Q1: What are the two main types of vulvar precancerous lesions?

The two major precancerous lesions of the vulva are High-Grade Squamous Intraepithelial Lesion (HSIL), which is typically HPV-associated, and Differentiated Vulvar Intraepithelial Neoplasia (dVIN), which is HPV-independent.

Q2: How do HPV-associated and HPV-independent vulvar precancers differ in prognosis?

Differentiated VIN (dVIN), the HPV-independent subtype, is significantly more aggressive and has a much higher rate of progression to invasive vulvar squamous cell carcinoma than the HPV-associated HSIL subtype.

Q3: What is the current standard treatment approach for High-Grade SIL (HSIL)?

Treatment for HSIL is varied and may include wide local excision, laser ablation, or topical immune-modulator therapy (e.g., Imiquimod). Doctors choose the option based on the lesion’s size, location, and multifocality.

References

  1. Welch KC et al. Precancerous Squamous Lesions of the Vulva. Obstet Gynecol. 2025 Dec 11. doi: 10.1097/AOG.0000000000006150. PMID: 41380160.
  2. Katayoon S, et al. Diagnostic Criteria for Differentiated Vulvar Intraepithelial Neoplasia and Vulvar Aberrant Maturation. Mod Pathol. 2017 Jul;30 Suppl 1:S11-S21.
  3. Machado AR, et al. The main differences between vulvar intraepithelial neoplasia and vulvar intraepithelial lesion. Obstet Gynecol Int J. 2020;11(5):323–326.
  4. Vulval intraepithelial neoplasia (VIN). Squamous intraepithelial lesion (SIL). DermNet. Accessed 2025 Dec 12.