Extramammary Paget's Disease of the Vulva
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Direct answer
Extramammary Paget's disease of the vulva is an uncommon intraepidermal adenocarcinoma that presents as a red, velvety, sharply demarcated and often itchy plaque. Its diagnostic feature is the Paget cell, a large cell with pale cytoplasm seen within the epidermis on biopsy. It may be associated with an underlying internal or cutaneous adenocarcinoma, and wide local excision with clear margins is the standard treatment.
What you must remember
- Presentation: An itchy, red, velvety plaque with sharp borders, often on the labia majora, mons or perineum.
- Paget cell: A large cell with abundant pale cytoplasm and pleomorphic nuclei, lying within the epidermis.
- Stains: Paget cells are periodic acid-Schiff positive and diastase resistant.
- Immunohistochemistry: Primary disease is typically CK7 positive and CK20 negative, which helps separate it from gastrointestinal origin.
- Primary disease: It has no underlying internal malignancy and arises in the skin itself.
- Secondary disease: It is associated with an adenocarcinoma of the anorectum, urinary tract or other genital site.
- Treatment: Wide local excision with clear margins is standard, and Mohs surgery is used in some centres.
- Recurrence: Recurrence is common because the intraepidermal spread often extends beyond the visible lesion.
A pathway from the plaque to excision
Extramammary Paget's disease is diagnosed on biopsy and treated by mapping the extent before excision. The steps below move from the visible plaque to long-term follow-up.
- Biopsy the plaque: A punch biopsy from the most active edge confirms Paget cells within the epidermis. Clinical appearance alone is never sufficient for diagnosis.
- Stain the section: Periodic acid-Schiff and diastase staining, with CK7 and CK20 immunohistochemistry, help separate primary from secondary disease.
- Search for an internal cancer: Secondary disease requires evaluation of the anal canal, rectum, urethra and bladder. Colonoscopy and cystoscopy are used as clinically indicated.
- Map the extent: Biopsies from the margins define the lesion, because subclinical intraepidermal spread is common. Inguinal nodes are examined as part of the assessment.
- Excise with clear margins: Wide local excision is performed to achieve clear margins, and Mohs micrographic surgery is used in some centres. The surgical plan should reflect the mapped extent.
- Follow up for recurrence: Lesions are monitored for recurrence and for the appearance of an internal malignancy. Follow-up is long-term because recurrence is common.
Traps students fall into
Questions here test the diagnostic pathway and the distinction from look-alike dermatoses.
- Trap: Diagnosing vulval Paget's disease from the rash alone. Correct: Biopsy showing Paget cells is required, since dermatoses such as lichen simplex chronicus can look similar.
- Trap: Treating extramammary Paget's disease with topical steroids as a simple dermatosis. Correct: It is an intraepidermal adenocarcinoma that needs excision with clear margins.
- Trap: Confusing extramammary Paget's disease with squamous Bowen disease. Correct: Paget cells, PAS-positive and diastase-resistant, define extramammary Paget's disease, whereas Bowen disease shows squamous atypia.
Frequently asked questions
What features identify Paget cells in vulval extramammary Paget's disease?
Paget cells are large cells with pale, clear cytoplasm and pleomorphic nuclei, found singly or in clusters within the epidermis. They stain positive for periodic acid-Schiff and are resistant to diastase. Histology confirms the diagnosis of extramammary Paget's disease of the vulva.
How is primary extramammary Paget's disease different from secondary disease?
Primary extramammary Paget's disease has no underlying internal malignancy, whereas secondary disease arises from an associated adenocarcinoma of the anorectum, urinary tract or another genital site. Immunohistochemistry and a search for an internal cancer help distinguish the two. The distinction determines whether further investigation is needed.
Which investigations look for an associated cancer in extramammary Paget's disease?
Colonoscopy, cystoscopy and examination of the anal canal and urethra are used to search for an associated internal cancer. The choice depends on clinical features and the immunohistochemical profile. Finding a primary cancer changes the treatment and prognosis.
What is the standard treatment for vulval extramammary Paget's disease?
Wide local excision with clear margins is the standard treatment for vulval extramammary Paget's disease. Mohs micrographic surgery is used in some centres to achieve clear margins with tissue sparing. Recurrence is common, so long-term follow-up is needed after treatment.
Why does vulval extramammary Paget's disease often recur after excision?
Recurrence is common because intraepidermal spread often extends beyond the visible lesion, so margins may be inadequate. Residual Paget cells left after incomplete excision can regrow. Mapping the lesion with biopsies before surgery reduces this risk.