Extramammary Paget Disease (EMPD) **1. Definition and Overview:  Extramammary Paget Disease (EMPD) is a rare type of skin cancer that affects the epidermis and is characterized by the presence of Paget cells. These cells are atypical epithelial cells found in the skin's surface layer. EMPD typically occurs in areas with apocrine glands, such as the genital and perianal regions, but can also affect other areas. **2. Etiology and Pathogenesis:  Origin: EMPD is believed to originate from apocrine glands or their ducts, although the exact mechanism is not fully understood. It can arise de novo or be associated with an underlying malignancy, particularly adenocarcinoma in nearby tissues.  Association with Underlying Malignancy: In some cases, EMPD is associated with an internal malignancy, often a gastrointestinal or urogenital cancer. This association is seen in approximately 10-30% of cases, and it is important to investigate potential underlying malignancies. **3. Clinical Presentation:  Symptoms: EMPD typically presents as a chronic, eczematous or erythematous rash with pruritus (itchiness). The lesions may be scaly, crusted, or ulcerated, and are usually found in the vulvar, scrotal, perianal, or axillary regions. In rare cases, it can also affect the nipple (where it is termed Paget's disease of the nipple).  Progression: The disease often progresses slowly and may be mistaken for other dermatologic conditions, such as eczema or psoriasis, leading to potential delays in diagnosis. **4. Diagnosis:  Clinical Examination: Diagnosis begins with a detailed clinical examination of the affected area, noting the appearance and distribution of lesions.  Biopsy: A skin biopsy is essential for diagnosis. Histological examination reveals the presence of Paget cells, which are large, atypical cells with clear cytoplasm and a hyperchromatic nucleus, scattered throughout the epidermis.  Immunohistochemistry: Immunohistochemical staining can be used to confirm the diagnosis, with Paget cells typically expressing markers such as CK7 and CEA (carcinoembryonic antigen). **5. Treatment:  Surgical Excision: The primary treatment for EMPD is surgical excision of the affected skin. Complete removal of the lesions with clear margins is crucial to prevent recurrence.  Topical Therapies: In some cases, topical chemotherapy agents like 5fluorouracil or imiquimod may be used, especially when surgery is not feasible.  Radiotherapy: For patients who are not surgical candidates or have residual disease, radiotherapy can be considered as an adjunctive treatment. **6. Prognosis and Follow-Up:  Prognosis: The prognosis for EMPD is generally favorable when the disease is localized and completely excised. However, the prognosis may be less favorable if there is an underlying malignancy or if the disease recurs.  Follow-Up: Regular follow-up is essential to monitor for recurrence or metastasis. This typically includes periodic physical examinations and possibly imaging studies if there is suspicion of internal malignancy. Overall, EMPD is a rare and potentially challenging condition that requires a multidisciplinary approach to ensure effective treatment and management. Early diagnosis and appropriate intervention are key to achieving the best outcomes for patients with this disease.