Abstract
BACKGROUND: Extramammary Paget's disease (EMPD) is a rare skin cancer that arises in areas rich in apocrine glands, such as the genital, perineal, and perianal regions. The gold standard for diagnosis is the histopathological study of a biopsy, and the standard treatment is wide surgical excision. Once the histopathological diagnosis of EMPD has been established, high frequency ultrasound (HFUS) has shown potential as a complementary non-invasive method useful for the initial assessment and EMPD's management. HFUS provides information about lesion extent, thickness, depth of invasion and vascularity throughout, as well as lymph node metastasis. We report two cases of EMPD in which HFUS proved useful for both diagnosis and treatment monitoring. KEY FINDINGS: Case 1: A 72-year-old woman with perianal EMPD who was not a candidate for surgery due to the risk of loss of sphincter function. Initial photodynamic therapy (PDT) resulted in partial improvement, and HFUS revealed persistent disease, leading to a switch to topical imiquimod, which was ultimately followed by CO(2) laser treatment after further HFUS-proven progression.Case 2: A 70-year-old man with inguinal EMPD underwent HFUS imaging, which showed epidermal involvement without dermal invasion throughout the entire lesion. Surgical excision was performed, confirming the HFUS findings. DISCUSSION: These cases highlight the role of HFUS as a complementary tool to biopsy for the initial assessment and follow-up of EMPD, especially when surgery is contraindicated or must be carefully planned. HFUS provides a detailed assessment of lesion characteristics critical for prognosis and therapy adjustments. The non-invasive nature, cost-effectiveness and ability to monitor treatment response make it a valuable adjunct to traditional diagnostics and to guide individualised management.