Squamous Neoplasms of the Vulva

Clinical Features

The spectrum of LSIL in the vulva includes exophytic and flat lesions. Exophytic condyloma (condyloma acuminatum) is a benign proliferative squamous lesion caused by HPV low-risk serotypes 6 and 11. Nearly one million patients are affected each year, the majority of whom tend to be young, sexually active women. Most lesions present as exophytic bumps in moist areas of the vulva but may be seen anywhere in the anogenital region ( Fig. 2.1 ). Flat condyloma (VIN I) can be caused by low-risk or high-risk HPV. The vast majority of VIN I regress without intervention. About 30-50% of patients have an associated HPV infection in the cervix.

Microscopic Features

Condyloma acuminatum typically displays an exophytic papillary architecture, easily appreciable at low-power magnification ( Fig. 2.2A ). Epithelial projections have different sizes and shapes but tend to have a convex and bulbous appearance with smooth inner (stromal) and outer (surface) borders. Flat condyloma (VIN I) lacks the papillary architecture of exophytic condyloma. Both exophytic and flat lesions show acanthosis, hyperkeratosis (with and without parakeratosis), and hypergranulosis (accentuated in the papillary spires). The most characteristic feature is the presence of viral cytopathic changes in the superficial epithelial layers which include nuclear enlargement with hyperchromasia, irregular (“raisinoid”) nuclear membranes, and perinuclear halos ( Fig. 2.2B ). Such changes, termed “koilocytosis”, are invariably seen but can be focal and less prominent than in cervical HPV-related lesions, particularly in regressing lesions or those previously treated pharmacologically. These “understated” koilocytes can be identified by their perinuclear halos, occasional binucleation, and nuclear membrane irregularities ( Fig. 2.3 ). The basal epithelium can be hyperplastic, but importantly retains nuclear polarity and uniformity . Mitotic figures should be morphologically normal and confined to the lower third of the epithelium. In patients that have undergone topical treatment with podophyllin, mitoses and apoptotic bodies may be conspicuous.

Differential Diagnosis

Fibroepithelial stromal polyps typically lack the acanthosis that is seen in condyloma; however, the distinction between the two may be difficult as koilocytosis can be subtle. Fibroepithelial stromal polyps often contain bland, multinucleated stromal cells and will lack significant epithelial alterations. In addition, detection of HPV DNA by PCR or in situ hybridization may be helpful in differentiating between these two histologically similar lesions. Seborrheic keratosis can be identified by their “keratin horn cysts” and striking basal cell hyperplasia but may be confused with condyloma due to the generalized acanthosis. Of note, HPV has been detected in cases of vulvar seborrheic keratosis, and some regard this entity as a variant of condyloma, particularly in young women. High grade vulvar intraepithelial neoplasia and squamous cell carcinoma with exophytic (“warty”) growth can be differentiated from condyloma by the presence of significant nuclear atypia in the lower epithelial layers and by the presence of mitoses throughout the epithelial thickness ( Fig. 2.4 A,B ). The distinction is mainly based on morphology, and it is important to remember that VIN1 can show p16 overexpression and harbor high-risk HPV types. Verrucous carcinoma , a rare and poorly understood form of vulvar squamous cell carcinoma, can be difficult to distinguish from condyloma, especially in small biopsies with poor representation of the tumor base. Unlike condyloma, verrucous carcinoma has endophytic growth into the underlying stroma with a more bulbous, broad-front interface; likewise, the superficial aspect also displays box-shaped projections that lack koilocytosis. If uncertainty remains, the possibility of verrucous carcinoma should be excluded through clinical correlation and complete surgical excision. Lichen simplex chronicus displays acanthosis, and may occasionally be verruciform, but lacks koilocytosis.

Prognosis and Therapy

Condyloma acuminata are benign, but many patients may suffer a protracted clinical course with multiple recurrences. Most lesions will spontaneously regress, but it is thought that the viral infection persists in a subclinical state. External factors that modulate cell-mediated immunity (immunosuppression, pregnancy, and smoking) may result in recurrence. Cases of condyloma progressing to a high-grade intraepithelial lesion or carcinoma have been reported; nonetheless, condylomata have very little, if any, risk of progression to squamous cell carcinoma, thus treatment is usually for symptomatic or cosmetic reasons. Podophyllin may be used for small, isolated lesions, while more potent topical medications, cryotherapy, laser ablation, and surgery may be considered for large or chronic lesions.

Flat condyloma/VIN I frequently regresses spontaneously, and close observation suffices in most patients. Persistent symptomatic lesions are treated with laser ablation or topical therapy (Aldara).

Clinical Features

The peak incidence of vulvar HSIL is in the early to mid-40s; however, incidence in patients in their 20s and 30s is rapidly increasing, likely due to an earlier onset of sexual activity in younger generations. Risk factors are similar to those for development of cervical squamous intraepithelial lesions including smoking and immunosuppression; not surprisingly given a shared pathogenesis with high-risk HPV infection, many patients with vulvar disease also have associated cervical precancers. If symptomatic, patients most commonly complain of pruritus, discomfort or a burning sensation in the affected area; pain and dyspareunia may occur particularly if the fourchette is affected. In up to 50% lesions are asymptomatic and discovered on self- or routine gynecologic examination. They appear as irregular macular areas of discoloration or plaques ( Fig. 2.5 ).

Microscopic Features

HSIL can be recognized on low power examination by its increased nuclear density and loss of maturation in comparison to normal squamous epithelium; in addition, there is often loss of polarity of the basal layer. At higher power, significant squamous nuclear atypia is seen involving the basal and upper epithelial layers ( Fig. 2.6 A,B ). Atypia is characterized by nuclear enlargement, hyperchromasia, and a variable degree of pleomorphism; dyskeratotic cells may be seen. These changes reflect the lack of maturation induced by the actively oncogenic virus. The nuclear atypia may only involve the bottom two-thirds of the epithelium and some residual maturation can be appreciated (lesions with this appearance were previously classified as VIN II) ( Fig. 2.7 ); some also show involvement of the superficial third of the epithelial thickness with complete loss of squamous maturation (previously classified as VIN III). Mitoses can involve the upper epithelial layers and may be abnormal. Abrupt squamous maturation, which can be quite pronounced, may be observed if there are superimposed irritative changes reflective of lichen simplex chronicus (acanthosis, hyperkeratosis, and parakeratosis).

Ancillary Studies

Most cases of HSIL will be readily diagnosed on routine H&E examination. In challenging cases, particularly those with superimposed lichen simplex chronicus, the use of p16, which is a surrogate marker for high-risk HPV infection, may be used to confirm the diagnosis. Only strong nuclear and cytoplasmic staining in a “block”-like pattern should be considered positive with a lower limit of positivity of at least 20 contiguous cells in basal and parabasal epithelium; most cases will show near or full thickness staining. The exception is those cases with superimposed lichen simplex chronicus where the staining may be limited to the lower layers of the epithelium but should still be strong and in a “block”-like pattern. It is important to keep in mind that strong but focal staining may sometimes be seen in reactive changes and thus strong, focal staining should be interpreted with caution. Ki-67 is typically strongly positive in all epithelial layers but is a marker of limited value in isolation as reactive changes can show overlapping patterns. HSIL with superimposed lichen simplex chronicus may be positive for p53, but positivity is in the parabasal, as opposed to basal, epithelium.

Differential Diagnosis

Candida infection may sometimes mimic HSIL as it may also result in acanthosis, nuclear enlargement, and hyperkeratosis; however, the presence of spongiosis and lack of nuclear crowding, hyperchromasia, and p16 positivity aids in this distinction. Of note, the presence of even rare neutrophils within the epithelium should serve as a trigger to consider periodic acid–Schiff with diastase or GMS stains which will highlight the fungal organisms. In a patient with pruritis, the use of special stains may be warranted to exclude the possibility of fungal infection even in the absence of appreciable neutrophilic infiltrates. Seborrheic keratosis displays acanthosis and a basaloid proliferation of cells that fills the epithelial layers and thus may mimic HSIL. The former is characterized by presence of keratin cysts and absence of nuclear atypia and p16 overexpression; of note, some vulvar seborrheic keratoses may be associated with low-risk HPV and p16 may show patchy positivity. Pseudobowenoid papulosis is an uncommon variant of a low-grade squamous intraepithelial lesion that manifests with greatly increased numbers of apoptotic cells in all layers of the epithelium. These dying cells may mimic mitotic figures and their presence in the upper epithelial layers may cause concern for HSIL. Similar to seborrheic keratosis, these lesions will contain only mild atypia and are negative or at most show patchy weak positivity for p16.

LSIL , either exophytic or flat, can be distinguished from HSIL by the preservation of epithelial maturation and absence of basal nuclear atypia in the former. According to LAST recommendations, p16 can be used in challenging situations as it is stated that overexpression will support a diagnosis of HSIL; however, the reader is cautioned that flat morphologically low-grade lesions may be secondary to high-risk HPV and can display p16 overexpression. dVIN is characterized by significant nuclear atypia; moreover, a basaloid variant has been described, which morphologically overlaps with HSIL. Unlike HSIL, atypia in dVIN is usually restricted to basal layers, and is associated with retained (albeit abnormal) maturation seen in the form of acanthosis, elongation and fusion of rete ridges, acantholysis, abnormal keratinization, and dyskeratotic cells. dVIN typically lacks p16 overexpression; conversely, p53 staining is abnormal (strong nuclear labeling involving basal epithelium and extending to upper layers). HSIL frequently involves skin adnexal structures, which may mimic invasive carcinoma ; a smooth outer contour of the suspicious focus with a basaloid morphology, maintenance of cell polarity with absence of paradoxical maturation at the epidermal-dermal interface argues against stromal invasion and is more in keeping with adnexal involvement ( Fig. 2.8 ).

Prognosis and Therapy

HSIL is associated with a high rate of recurrence, especially in cases with positive or narrowly excised margins. Additionally, it carries a risk of developing invasive carcinoma if left untreated. It is not possible to know the precise risk of progression as most patients are treated; however, a study by Jones et al showed ∼4% of women treated for HSIL developed invasive squamous cell carcinoma (related to positive margins and “new” disease, i.e., field related effect) while a study by Chafe et al found that ∼19% of women treated for HSIL had unsuspected invasive squamous cell carcinoma. Thus, surgical excision with negative margins is the mainstay of treatment; cryotherapy or laser ablation may be used in small lesions or in multifocal lesions not amenable to surgical resection. Topical therapy with Aldara is a therapeutic consideration in small lesions. Similar to cervical squamous intraepithelial lesions, regression of HSIL may occur, although less commonly. Patients who have had spontaneous regression are typically young (median 19 years), of non-European ethnicity, and present with asymptomatic, pigmented, multicentric disease.