Vulvar squamous cell carcinomas (VSCC) comprise approximately 90% of all vulvar malignancies. Unlike cervical SCC, which are predominantly human papilloma virus (HPV) positive, only a minority of VSCC are HPV positive – on the order of 15%-25% of cases. Most cases occur in the setting of lichen sclerosus and are HPV negative.
Lichen sclerosus is a chronic inflammatory dermatitis typically involving the anogenital area, which in some cases can become seriously distorted (e.g. atrophy of the labia minora, clitoral phimosis, and introital stenosis). Although most cases are diagnosed in postmenopausal women, LS can affect women of any age. The true prevalence of lichen sclerosus is unknown. Recent studies have shown a prevalence of 1 in 60; among older women, it can even be as high as 1 in 30. While lichen sclerosus is a pruriginous condition, it is often asymptomatic. It is not considered a premalignant condition. The diagnosis is clinical; however, suspicious lesions (erosions/ulcerations, hyperkeratosis, pigmented areas, ecchymosis, warty or papular lesions), particularly when recalcitrant to adequate first-line therapy, should be biopsied.
VSCC arises from precursor lesions or high-grade vulvar intraepithelial neoplasia (VIN). The 2015 International Society for the Study of Vulvovaginal Disease nomenclature classifies high-grade VIN into high-grade squamous intraepithelial lesion (HSIL) and differentiated VIN (dVIN). Most patients with high-grade VIN are diagnosed with HSIL or usual type VIN. A preponderance of these lesions (75%-85%) are HPV positive, predominantly HPV 16. Vulvar HSIL (vHSIL) lesions affect younger women. The lesions tend to be multifocal and extensive. On the other hand, dVIN typically affects older women and commonly develops as a solitary lesion. While dVIN accounts for only a small subset of patients with high-grade VIN, these lesions are HPV negative and associated with lichen sclerosus.
Both disease entities, vHSIL and dVIN, are increasing in incidence. There is a higher risk and shortened period of progression to cancer in patients with dVIN compared to HSIL. The cancer risk of vHSIL is relatively low. The 10-year cumulative VSCC risk reported in the literature is 10.3%; 9.7% for vHSIL and 50% for dVIN. Patients with vHSIL could benefit from less aggressive treatment modalities.
Patients present with a constellation of signs such as itching, pain, burning, bleeding, and discharge. Chronic symptoms portend HPV-independent lesions associated with lichen sclerosus while episodic signs are suggestive of HPV-positive lesions.
The recurrence risk of high-grade VIN is 46%-70%. Risk factors for recurrence include age greater than 50, immunosuppression, metasynchronous HSIL, and multifocal lesions. Recurrences occur in up to 50% of women who have undergone surgery. For those who undergo surgical treatment for high-grade VIN, recurrence is more common in the setting of positive margins, underlying lichen sclerosis, persistent HPV infection, and immunosuppression.
Management of high-grade VIN is determined by the lesion characteristics, patient characteristics, and medical expertise. Given the risk of progression of high-grade VIN to cancer and risk of underlying cancer, surgical therapy is typically recommended. The treatment of choice is surgical excision in cases of dVIN. Surgical treatments include CO2 laser ablation, wide local excision, and vulvectomy. Women who undergo surgical treatment for vHSIL have about a 50% chance of the condition recurring 1 year later, irrespective of whether treatment is by surgical excision or laser vaporization.
Since surgery can be associated with disfigurement and sexual dysfunction, alternatives to surgery should be considered in cases of vHSIL. The potential for effect on sexual function should be part of preoperative counseling and treatment. Women treated for VIN often experience increased inhibition of sexual excitement and increased inhibition of orgasm. One study found that in women undergoing vulvar excision for VIN, the impairment was found to be psychological in nature. Overall, the studies of sexual effect from treatment of VIN have found that women do not return to their pretreatment sexual function. However, the optimal management of vHSIL has not been determined. Nonsurgical options include topical therapies (imiquimod, 5-fluorouracil, cidofovir, and interferon) and nonpharmacologic treatments, such as photodynamic therapy.
Imiquimod, a topical immune modulator, is the most studied pharmacologic treatment of vHSIL. The drug induces secretion of cytokines, creating an immune response that clears the HPV infection. Imiquimod is safe and well tolerated. The clinical response rate varies between 35% and 81%. A recent study demonstrated the efficacy of imiquimod and the treatment was found to be noninferior to surgery. Adverse events differed, with local pain following surgical treatment and local pruritus and erythema associated with imiquimod use. Some patients did not respond to imiquimod; it was thought by the authors of the study that specific immunological factors affect the clinical response.
In conclusion, high-grade VIN is a heterogeneous disease made up of two distinct disease entities with rising incidence. In contrast to dVIN, the cancer risk is low for patients with vHSIL. Treatment should be driven by the clinical characteristics of the vulvar lesions, patients’ preferences, sexual activity, and compliance. Future directions include risk stratification of patients with vHSIL who are most likely to benefit from topical treatments, thus reducing overtreatment. Molecular biomarkers that could identify dVIN at an early stage are needed.
Dr. Jackson-Moore is associate professor in gynecologic oncology at the University of North Carolina at Chapel Hill. Dr. Tucker is assistant professor of gynecologic oncology at the university.
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