Introduction: Doctors are usually reluctant to perform a vulvar biopsy on a patient with non-specific chronic vulvitis - especially because of the rarity of vulvar malignancy in young women - until the lesion is suspected of being malignant. Therefore, most cases of extramammary Paget's disease (EMPD) were originally misdiagnosed as chronic and recurrent vulvar lesions. Late diagnosis of invasive lesions occurring in elderly females have resulted in cases of death. Case: A 37-year-old patient showed an extended lesion on the vulva and perineum. In addition, abnormal cells were found from a vulvar scrape smear, and a following punch biopsy was used to diagnose and determine the extension of the disease. Conclusion: Diagnosis and demarcation of EMPD remain difficult due to the multi focal lesions and subtle nature of the disease. Brush sampling taken from suspicious areas can be a guide for multiple biopsies to demarcate the lesion before major surgery. A brush biopsy is presented as a first-step method to detect vulvar malignancy.