If the area looks suspicious, the main test is a biopsy. That means a small piece, or sometimes the whole spot, is removed and checked under a microscope. This helps confirm whether it is skin cancer and what type it is. If cancer is found, more tests may be advised depending on how deep or advanced it looks. I used this page to keep the answer simple and related to melanoma skin cancer: https://uhapo.co.in/melanoma-skin-cancer/