Diagnosing skin cancer starts with checking out a bump, spot, sore, colored area, or other mark on your skin. Any area of skin that doesn't look normal and may have disease is called a lesion. Most lesions are not cancer, but some may be cancer. You may need to see a dermatologist. This is a doctor with special training in diagnosing and treating skin problems.

If your doctor thinks you might have nonmelanoma skin cancer, you will need certain exams and tests to be sure. Diagnosing skin cancer starts with your doctor asking you questions. They will ask you about your health history, symptoms, risk factors, and family history of disease. Your doctor will also give you a physical exam and skin exam.

Make sure that you tell your doctor if you've had skin cancer in the past. Also tell them if anyone in your family has had skin cancer.

Some skin lesions may look suspicious for skin cancer and need to be removed. A biopsy is a small piece (sample) of tissue that's taken to be checked in a lab. Your doctor will likely take a biopsy of any lesion that may look like cancer.

The different types of biopsies include:

• Shave biopsy. This type of biopsy removes the top layers of skin of a lesion. This type of biopsy is often used for very flat skin lesions. Your doctor will inject the area with numbing medicine and then shave off the lesion with a sharp blade. Sometimes part of the lesion may be left behind. You may need another procedure to remove it completely.
• Punch biopsy. This type uses a special tool to take a deep sample of skin. This may be done if the lesion is small or when just a part of a larger lesion needs more study. Or it may be done if your doctor wants more information about the undersurface of a lesion. The tool is like a very small paper hole punch or apple corer. It removes a short cylinder of tissue. First, your doctor uses a numbing medicine on the area. The punch tool is turned on the surface of the skin until it cuts through all the layers of skin. This includes the dermis, epidermis, and the most superficial parts of the skin fat (subcutis). The doctor removes the biopsy sample and may then stitch together the edges of the wound.
• Excisional biopsy. This type of biopsy is often used when your doctor needs a wider or deeper piece of the skin. The entire lesion and sometimes part of the surrounding skin is removed. First, your doctor uses numbing medicine on the area. Then the doctor uses a surgical knife (scalpel) to remove a full-thickness wedge of skin. The wound is closed with surgical thread (stitches), staples, tape, or surgical glue. What the doctor uses depends on how large the incision is and where it is.
• Incisional biopsy. This procedure is like an excisional biopsy. But only part of the lesion is removed.

A biopsy sample is sent to a lab, where a doctor called a pathologist looks at it under a microscope.

If skin cancer is found, the pathologist will look at certain features of the lesion. These include the type of skin cancer and the thickness of the lesion. This can help your doctor figure out the extent (stage) of the skin cancer. The stage of skin cancer helps your doctor decide about treatment choices.

Your biopsy results will likely be ready in a few days to a week or so. Your doctor will give you the results. They will talk with you about other tests or treatments that you may need if skin cancer is found. Make sure you understand the results and what follow-up you need.