Asian Journal of Research in Dermatological Science

Background: Extramammary Paget disease is a rare cutaneous adenocarcinoma that predominantly affects apocrine gland-bearing areas and often presents with nonspecific eczematous, erythematous, or erosive lesions. Its clinical resemblance to common inflammatory and infectious dermatoses can lead to delayed diagnosis. Moreover, the microscopic extent of the disease may exceed its clinically visible margins, creating additional diagnostic and therapeutic challenges.

Aims: To report a case of extensive perineal extramammary Paget disease (EMPD) mimicking a chronic inflammatory dermatosis and to highlight the clinical, dermoscopic, histopathological, and therapeutic features that contributed to diagnosis and management.

Presentation of Case: A 61-year-old man presented with an approximately 18-month history of progressively extending pruritic lesions involving the inguinal folds, genital region, perineum, and perianal area. The lesions had initially been treated as a presumed fungal infection and later as eczema, without clinical improvement. Examination showed extensive erythematous-squamous and lichenified plaques with macerated and focally erosive areas. Dermoscopy revealed polymorphous rounded and lobulated whitish structures on a pink-to-erythematous background, fine pink partitions, and focal superficial erosions. Histopathology established the diagnosis of EMPD. Staging did not identify a definite associated internal malignancy. Wide surgical excision with reconstruction and a temporary protective colostomy was performed. The surgical specimen showed perineal Paget disease in situ with diffuse CK7 positivity and no invasive component. One lateral margin was involved and the remaining lateral margins were less than 1 mm from the lesion; adjuvant radiotherapy was therefore proposed.

Discussion: EMPD is a rare cutaneous adenocarcinoma of apocrine-rich areas and often resembles benign inflammatory or infectious dermatoses. Persistent treatment-resistant lesions at characteristic sites should prompt biopsy. Dermoscopy may provide useful clues but histopathology remains essential. The microscopic extent of EMPD may exceed clinically visible borders, complicating surgical margin control.

Conclusion: This case illustrates the risk of delayed diagnosis in chronic eczematous genital and perineal lesions and the value of integrating clinical examination, dermoscopy, histopathology, staging, and multidisciplinary management.