Paget’s disease is a malignant tumor that occurs in the nipple area and is a special type of breast cancer, accounting for about 0.7 to 3% of all breast cancers. Perianal Paget’s Disease (PPD) belongs to extramammary Paget’s disease, which is a rare malignant tumor. Disease recognition process: ①James Paget first reported Paget’s disease in 1874; ②Croker first reported extramammary Paget’s disease occurring in the scrotum and penis in 1889. (iii) Perianal Paget’s disease was first reported by Dafter and Coculillard in 1893. A total of 31 cases were reported in the literature by 1973, rising to 96 cases by 1988 and a total of 114 cases worldwide by 1993. 13 cases were summarized by the Mayo Clinic between 1970 and 1995 (6) and 27 cases were summarized by the Memorial Sloan Kettefing Cancer Center in New York between 1950 and 2000 (7). Kettefing Cancer Center in New York summarized a total of 27 cases reported during the 50-year period (7). A search of the domestic literature also showed only 27 cases from 1994 to 2005. The incidence of perianal Paget’s disease tends to occur in patients of advanced age, and the ratio of men to women in the literature is not uniform or even opposite, which may be related to the small number of cases. Pathological origin There is no uniform understanding of the origin of the disease, but it tends to originate from sweat cells. Because EMPD mostly occurs in the axilla, perineum, external genitalia, perineum and other areas with well-developed sweat glands, very rarely it has also been reported in the lower esophagus, stomach, rectum, bladder and cervix. It is believed that there are three sources of Paget’s cells in EMPD: (1) secretory or exocrine adenocarcinoma of parietal pulp originating from below the tissue, especially sweat adenocarcinoma; (2) adenocarcinoma in situ originating from within the epidermis, also known as intraepithelial neoplasia; and (3) caused by concomitant simultaneous or heterochronic spread of carcinomas from adjacent internal organs into the epidermis. Staging: PPD is divided into four stages: Stage I: limited perianal lesions without associated tumors; Stage IIA: limited perianal lesions with adnexal skin tumors; Stage IIB: limited perianal lesions with anorectal tumors; Stage III: local lymph node metastasis with associated tumors; Stage IV: distant metastasis. Pathological histology: typical Paget’s cell changes, with large, round or ovoid cells, abundant cytoplasm, light staining, obvious nucleoli, and tumor cells often distributed in groups or singly in the epidermis. Diagnosis: It mainly relies on histocytological examination to find Paget’s cells in the epidermis. ① Clinical manifestations: The main manifestations are anal pruritus, blood in stool or change in the number of stools, and often a history of anal pruritus that has not been cured for a long time. ② Signs: The lesions are found to have still clear borders, generally with a brown appearance, central flushing or erosion, their surfaces covered with scales or scabs, and sometimes local skin thickening in the form of nodules or masses. Differential diagnosis: Pay attention to the differentiation with some rare diseases around the anus, such as Bowen’S disease, Paget-like malignant melanoma, etc. Treatment: The treatment of PPD depends on the clinical stage of PPD and the selection of appropriate treatment methods combined with the actual clinical situation. In terms of staging, PPD is divided into four stages: stage I: local enlargement resection; stage IIA: local enlargement resection; stage IIB: abdominal perineal surgery; stage III: radical abdominal perineal surgery plus radiotherapy and inguinal lymph node dissection if possible; stage IV: palliative care. If the lesion is large or circumferential, the anal canal should be resected circumferentially, with intraoperative freezing, and depending on the extent of the skin defect, skin grafting or flap transposition, or even bowel diversion, should be performed. Follow-up reveals that the S-shape is more aesthetically pleasing than the rectangular flap and that no anal canal stricture occurs, so adequate preoperative flap design and good plastic surgery skills are required. If the lesion is associated with an anal canal or rectal tumor, abdominal perineal surgery should be performed. If the tumor infiltrates into the reticular layer of the dermis or subcutaneous tissue, lymph node dissection should be performed if lymph node metastasis is clinically suspected and confirmed by biopsy. Some scholars advocate the use of non-surgical treatment for this disease, including radiotherapy, chemotherapy, combination of radiotherapy and chemotherapy, phototherapy, and Mohs chemosurgery, etc. Although successful cases of these methods have been reported, they are not recommended as treatment norms because of the small number of cases. For those who are not suitable for surgery, or who have recurred after surgery, these methods may be chosen as the first choice or as an adjuvant treatment. Comorbidities and prognosis: The proportion of perianal Paget’s disease with colorectal cancer is high, and the cancer may be concurrent or heterochronic, the latter mostly refers to patients who were first treated for perianal Paget’s disease and found to have cancer during follow-up. Therefore, careful and complete examination, such as rectal examination and electronic colonoscopy, must be performed before treatment. At the same time, close follow-up must be performed after surgery, because it is easy to recur locally after surgical resection, and the recurrence rate is as high as 31-61%, even for those with negative margins, there is a recurrence rate of 26%. Its prognosis is related to the depth of infiltration, lymph node metastasis and positive margins, so long-term follow-up and resection after recurrence are especially critical. In conclusion, perianal Paget’s disease is an extremely rare malignant tumor, which is not well understood in clinical practice and can be easily misdiagnosed. The definitive diagnosis lies in the histocytological examination of suspected cases, and the treatment is mainly surgical, supplemented by radiotherapy and/or chemotherapy if necessary.