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Histology of vulvar cancer

Vulvectomy with squamous-cell carcinoma.
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Our pathologists receive small punch biopsies, resected specimens, boat-formed  resections and vulvectomy specimens for histopathological examination. The punch biopsies are placed and whole-mounted. It is important that the surgical specimens are properly oriented and pinned on a board by the gynecologist . This will allow the pathologists to sample relevant sections from the specimen so that the pathologist can stage the tumor and evaluate the resection margins by lightmicroscopy . In addition to tumor type, the pathologists report the histological grade, largest tumor diameter, depth of infiltration or tumor thickness, vascular infiltration, distance to resection margins, presence of pre-invasive lesions and lichen sclerosus.

Benign tumors

Genital warts (condylomata accuminata) are common  . Genital warts vary in size from a few millimeters to a single tumor of multiple centimeters, known as giant condyloma. Giant condyloma should be surgically resected to exclude variants of highly-differentiated squamous-cell carcinoma. 

Benign tumors may originate from skin adnexa structures and from soft tissue (lipoma, fibroepithelial polyp, leiomyoma, granular cell tumor, cell-rich angiofibroma, and angiomyofibroma). Aggressive angiomyxoma   have an aggressive disease course with a high risk for recurrence. Patients with soft tissue tumors must be referred to a tertiary hospital with experience in treating such rare cases.

Pre-stages

Squamous-cell carcinoma in the vulva developes via pre-invasive lesions called vulva intraepitelial neoplasia (VIN). There are two types, differing both in treatments and in etiology.

Differentiated VIN.
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Differentiated VIN (previously called atypical squamous-cell hyperplasia) is a precursor forthe most frequently occurring keratinizing squamous-cell carcinoma. Differentiated VIN is not associated with HPV and occurs usually in elderly women, with lichen sclerosus, which is a degenerative skin condition . Differentiated VIN can be difficult to recognize by pathologists with little experience in this area because the atypia is minimal. Differentiated VIN are often misdiagnosed as a benign lesion (squamous-cell hyperplasia with hyperkeratosis). These are, however, high-grade lesions that must be treated with surgery to prevent progression into squamous-cell carcinoma.

High-grade VIN.
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High-grade VIN is often much easier to recognize; they are not graded, but are equivalent to what was previously classified as VIN 2-3 or usual VIN. These are associated with high-risk HPV infection. If the biopsy excludes carcinoma, small lesions can be treated with immune-stimulating cream. To subclassify the VIN lesion, HPV and immunohistochemical analysis may be helpful to render the correct diagnosis. Differentiated VIN is negative for HPV and often positive for p53 in the lower part of the squamous epithelium . High-grade VIN is positive for HPV 16 or one of the other high-risk HPV types, and shows strong immunhistochemical staining for p16 through the entire thickness of the epithelium .

Malignant tumors

Malignant vulvar tumors are classified according to the 2014 WHO classification. Approximately 85 % are squamous-cell carcinoma, 10% are malignant melanoma, and 5% are adenocarcinoma, basal-cell carcinoma or sarcoma.

Keratinizing squamous-cell carcinoma.
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There are multiple types of squamous epithelial carcinoma, which vary in prognosis and etiology. The most frequent type is keratinizing squamous-cell carcinoma, which occurs in the highest age group, and is associated with differentiated VIN and lichen sclerosus. Squamous-cell carcinoma is graded according to the degree of nucleic atypia and keratinization . Verrucous carcinoma and papillary carcinoma are low-grade malignancies and are not associated with HPV. In small biopsies, these can be difficult to differentiate from giant condylomat. Basaloid carcinoma and condylomatous/warthy carcinoma are HPV-associated tumors that develop from high-grade VIN.

Malignant melanoma is the next most frequent malignant vulvar tumor after squamous-cell carcinoma. It occurs in the highest age group, and is often ulcerating at the time of diagnosis . Lentiginous types are the most frequent type , followed by nodular, superficial spreading and unclassifiable types.

Basal-cell carcinoma constitute 2-3% of the malignant vulvar tumors, the differential diagnosis is basaloid carcinoma, which has a much poorer prognosis. Paget's disease constitute about to 2 % of the vulvar neoplasms and are intraepithelial adenocarcinoma  .which may also involve the skin adnexa structures. Invasive adenocarcinoma in underlying dermis and subcutaneous tissue are rare. Adenocarcinoma in the anus or bladder must also be excluded immunohistochemistry and HPV analysis can be helpful to differenstiate the Pagetoid variant of high-grade VIN from Paget disease and malingnant melanoma in situ.

Carcinoma in the Bartholin's gland (most often adenocarcinoma) is rare, and must not be mistaken for bartholinitis. Cancer in Bartholin's gland is usually solid, while bartholinitis and Bartholin's cyst are cystic. Ultrasound may be helpful. Patients with solid tumors in Bartholin's gland should be referred for work-up and treatment at a center for gynecological cancers, and not preceded by surgical intervention by a local hospital. These tumors are located posterolateral on the outer labia and are not associated with HPV.

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