Extramammary Paget's disease (EMPD) is a rare neoplastic disease affecting areas rich in apocrine glands in the elderly. EMPD clinically resembles a benign inflammatory skin disease, and ill-defined tumor borders can lead to misdiagnosis and incomplete excision. Several prognostic factors have been reported, including nodule formation, tumor thickness, tumor invasion, lymphovascular invasion, and a perianal location, which are characteristic of primary tumors. EMPD typically presents as an in situ tumor spreading horizontally within the epidermis and then invading into the dermis as it transitions to a vertical growth phase. For this reason, tumor thickness, rather than tumor size, is correlated with patient prognosis. The best treatment for resectable EMPD is complete surgical removal of the tumor. EMPD sometimes has unclear tumor borders, and it can unexpectedly spread beyond its clinical boundaries. Surgical resection in such cases is often associated with tumor-positive margins, which can result in recurrence. However, surgical excision with wide margins may deteriorate patients' organ functions and quality of life. Mohs micrographic surgery may be ideal for controlling the surgical margins and minimizing the sacrifice of normal tissue, but this technique is not always feasible because of constraints associated with the medical environment. No standard treatment for unresectable or metastatic EMPD has been established. Although conventional chemotherapy has been used as the first-line treatment, it frequently causes adverse events, and consequently, targeted therapy will become more valuable in the near future.
Keywords: Extramammary Paget’s disease; Non-melanoma skin cancer; Targeted therapy.
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