Clinicopathological Analysis of 40 Cases of Extramammary Paget Disease: A Retrospective Study.

Background: Extramammary Paget Disease (EMPD) is a rare intra-epithelial malignancy often misdiagnosed due to diverse clinical manifestations. This study retrospectively analyzed the clinicopathological features of 40 EMPD patients to provide references for clinical practice. Methods: Clinical data of 40 patients with pathologically confirmed EMPD were collected, including demographics, clinical features, histopathological and immunohistochemical findings, treatments, and follow-up outcomes. Results: Of the 40 patients (27 males, 13 females; mean age 68.8 years), the most common onset location was the external genitalia (n = 33). Lesions primarily presented as erythema or red plaques (n = 38), with itching being the most common symptom (n = 26). Immunohistochemically, tumor cells were positive for CK7, CEA, and EMA, with positive rates of 70% for GCDFP-15 and 25% for CK20. Thirty-nine patients underwent surgical excision, and one received photodynamic therapy combined with radiotherapy. During follow-up after surgery, one patient with invasive features (tumor mass in the dermis) recurred but achieved remission after reoperation; the other 38 patients remained disease-free. Invasive EMPD was associated with a higher risk of recurrence. Conclusion: EMPD's varied presentations pose diagnostic challenges. Key diagnostic differentials include eczema, psoriasis, and melanoma, particularly for rare pigmented or depigmented variants. For clinicians, a high index of suspicion and prompt biopsy are crucial for early diagnosis. For pathologists, a comprehensive immunohistochemical panel is essential, while CK20's utility in distinguishing primary from secondary disease is limited and warrants further malignancy screening. Surgical excision remains the primary treatment, with alternative therapies effective for inoperable cases. Early diagnosis, appropriate treatment, and long-term follow-up are crucial for optimal prognosis.