Paget disease, also known as eczema-like carcinoma, is a specific type of carcinoma characterized by eczema-like lesions and large, dark-stained abnormal cells (Paget cells) in the epidermis, and is divided into two types: 1) breast Paget disease, which occurs in the nipple and areola; 2) extramammary Paget disease, which is commonly found in the distribution area of the acromegaly, such as the female genitalia, male genitalia, perianal area, and axilla. The pathogenesis of primary extramammary Paget’s disease is multifaceted, and it is believed that it may originate from cells in the opening of the parietal sweat duct or from multipotent cells differentiated in the epidermis towards the parietal sweat gland, and from there it expands downward along the breast duct and glandular epithelium, and eventually invades the connective tissue; upward it expands into the epidermis and forms Paget’s disease lesions. Epidermal lesions secondary to extramammary Paget disease often arise from deep rectal, endocervical, urethral, prostate, or bladder cancer metastasizing to the epidermis. Perineal lesions are complicated by adenocarcinoma of the rectum in 1/3 of cases. The disease mostly occurs in men and is rare in women. It usually occurs over the age of 50 and has a slow course with a duration of six months to more than 10 years. The lesions are usually found in the area of the parietal sweat glands, such as the scrotum, penis, labia majora and minora and vagina, and rarely in the perianal area, perineum or axilla. Most of the lesions are solitary, a few are multiple, and it is even rarer for them to occur in two areas simultaneously. Extramammary Paget disease can be secondary to the extension of adenocarcinoma, such as from the rectum to the perianal area, from the cervix to the female genital area, from the bladder to the urethra, glans or inguinal area, etc. It is called secondary extramammary Paget disease. On the other hand, long-standing extramammary Paget disease in the genital area may invade the cervix or urinary tract. The damage, like breast Paget disease, presents as well-defined red patches or plaques of varying sizes with narrow, slightly elevated margins, light brown in color, with central flushing, erosion or oozing, covered with scales or crusts, sometimes warty, nodular or papillomatous, with varying degrees of self-induced pruritus and, in a few cases, pain. The histopathological features are: 1, the epidermis has a single or nested arrangement of Paget cells, large, round or oval cells, no intercellular bridges, cells containing a large nucleus, cytoplasm rich and lightly stained, or even vacuolated. 2, Paget cells increase, the surrounding epidermal cells can be extruded into a network, especially the epidermal basal cells are often extruded into a thin band. 3, Paget cells PAS reaction positive, resistant to amylase. 4, The dermis is accompanied by chronic inflammatory cell infiltration. Diagnosis In elderly people over 50 years of age, eczema-like skin lesions occurring in the external genital area or the perianal area and other areas of the distribution of the parietal sweat glands that do not heal for a long time, with clear boundaries, basal infiltrates, a slow and persistent course, and ineffective treatment according to eczema, should be suspected of this disease, and pathological biopsy can confirm the diagnosis. Differential diagnosis 1, breast eczema usually occurs in both breasts, the edges are unclear, easy to recur, itching is obvious. Treatment according to eczema is mostly effective. 2, nipple erosive adenomatosis Early nipple erosion, often with plasma exudate, clinically very similar to breast Paget’s disease, late nipple nodular enlargement is easy to distinguish. Histopathology shows irregular dilated tubular structures extending downward from the epidermis, which can be distinguished. Bowen’s disease can occur in any part of the skin and mucosa, but rarely invades the nipple and areola, and histopathology shows epidermal dyskeratosis and multinucleated giant cells, unlike paget’s disease. Treatment Surgical excision should be the first choice, using the Mohs surgical technique. If the damage is large and accumulates in the groin and perineum, implantation is required. Secondary extramammary Paget’s disease should be treated accordingly to the primary disease. Recurrent cases may be re-surgically excised. Extramammary paget disease generally has a better prognosis than breast paget disease, but can be associated with invasive intradermal cancer. In secondary extramammary paget disease, the prognosis is poor.