Extramammary Paget’s disease (EMPD) is a rare skin neoplasia, perianal localization of which takes second place in frequency of occurrence among all other forms. Distinguished the primary form of EMPD, in which the cells of the infundibular region of the hair follicles and the nearby excretory ducts of the apocrine glands or pluripotent cells are the sourse of neoplasia, and the secondary form that develops by transepidermal spread of the malignant tumor from the underlying tissues. EMPD occurs in elderly, more often in women. The frequency of association of EMPD with malignant internal organs depends on the anatomical location of the lesion. EMPD is associated with malignant neoplasms of internal organs in an average of 29% of cases. So, EMPD in the genital area is often accompanied by urinary tract carcinomas, while perianal localization — with damage to the gastrointestinal tract. The early diagnosis of EMPD by a dermatologist is an actual problem, because EMPD patients for a long time may erroneously receive therapy for eczema, psoriasis, mycosis, vegetative pemphigus, familial benign pemphigus Gugerot—Haley—Haley, which prolongs the time for timely diagnosis of this neoplasia. The article describes a clinical case of delayed diagnosis of the perianal form of EMPD.