What is the recommended diagnostic and treatment approach for extramammary Paget’s disease of the scrotum?

Extramammary Paget's Disease of the Scrotum: Diagnostic and Treatment Approach

Primary Recommendation

Wide surgical excision with negative margins remains the definitive treatment for scrotal extramammary Paget's disease (EMPD), with resection margins of at least 2 cm for tumors >6 cm and consideration of photodynamic therapy (PDT) or CO2 laser-assisted PDT as adjunctive or alternative options when surgery is contraindicated 1, 2.

Diagnostic Workup

Initial Clinical Assessment

Look specifically for:

• Chronic erythematous, pruritic plaques on the scrotum that have been misdiagnosed as benign dermatoses (eczema, fungal infections)
• Mucous discharge from lesions 3
• Duration of symptoms (often prolonged due to diagnostic delays)

Dermoscopic Examination

• Characteristic finding: "red background with punctate vessels" 3

Histopathologic Confirmation

• Biopsy is mandatory for definitive diagnosis
• Immunohistochemistry profile to confirm:
  • CK7 positive (sweat gland origin)
  • GCDFP-15 positive (apocrine differentiation)
  • D2-40 (podoplanin) status indicates lymphatic invasion risk 3

Mapping Biopsy

• Perform mapping biopsies around the visible lesion to determine subclinical extension, as EMPD has a tendency for microscopic spread beyond visible margins 4, 2

Staging for Associated Malignancies

• Screen for underlying visceral malignancies, particularly in perianal EMPD (higher association than genital EMPD) 5
• Sentinel lymph node biopsy should be considered when dermal invasion is suspected 4
• Assess for nodal involvement as this significantly correlates with recurrence and mortality (HR=4.645) 2

Treatment Algorithm

For Localized, Operable Disease

Primary approach: Wide local excision

Margin Selection Based on Tumor Size:

• Tumors <6 cm: 2 cm margins acceptable (achieves 20% recurrence rate) 2
• Tumors >6 cm: >2 cm margins required (mean 2.5 cm) 2

Intraoperative Management:

• Frozen section analysis of margins intraoperatively
• Re-excise positive margins immediately 3
• Plan for complex closure with skin grafting or local flaps as genital defects often require reconstructive surgery 6

Alternative: Mohs micrographic surgery - considered by some as gold standard for extensive tumors, though wide local excision yields similar recurrence rates 6, 7

For Non-Surgical Candidates or Adjunctive Therapy

Photodynamic therapy (PDT) is the guideline-recommended non-surgical option:

• R20: Consider PDT for EMPD either before or after surgery 1
• R21: Consider CO2 laser prior to PDT for EMPD 1
• PDT is particularly useful where Paget cell infiltrate is less dense 1
• Pain may be a limiting factor (similar to erythroplasia of Queyrat) 1

Other non-surgical options (lower evidence):

• Topical imiquimod
• Radiotherapy (may be alternative for extensive disease) 7
• Laser therapy 6

For Metastatic or Unresectable Disease

First-line systemic therapy: Carboplatin/paclitaxel

• Recent case data shows median survival exceeding 41 months with this regimen 8
• Six cycles is the standard approach 8

Second-line options:

• Pembrolizumab (immune checkpoint inhibitor) - can be considered even with low CPS scores (CPS 5) after chemotherapy failure 8
• HER2-targeted agents (if HER2 positive) 9

Lymph node management:

• Lymph node dissection for regional metastases 4
• Consider radiation therapy after regional lymph node dissection 4

Critical Pitfalls to Avoid

1. Delayed diagnosis: EMPD mimics benign dermatoses. Biopsy any chronic scrotal erythematous plaque not responding to standard treatments.

2. Inadequate margins: Recurrence rates remain high (up to 50%) even with mapping biopsies 5. The correlation between tumor size and required margin is critical - don't use <2 cm margins for tumors >6 cm 2.

3. Missing nodal involvement: This is the strongest predictor of recurrence and mortality. Always assess lymph nodes clinically and consider sentinel node biopsy for invasive disease 2.

4. Inadequate screening for visceral malignancy: Secondary EMPD represents spread from underlying carcinoma. Complete staging workup is mandatory 4, 5.

5. Assuming negative margins mean cure: Even with negative margins, recurrence occurs frequently. Close surveillance is non-negotiable 10, 5.

Surveillance Protocol

• Regular follow-up to evaluate for disease recurrence or progression 10
• Recurrence rates of 21.2% reported even after complete excision 2
• Continue surveillance until multiple years disease-free (specific intervals not standardized due to disease rarity) 3