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Melanoma: Diagnosis

Diagnosing melanoma starts with checking out a mole or other mark on your skin. Your health care provider will examine your skin with the ABCDE rules in mind. This means looking at:

  • Asymmetry. One half of the mole does not match the other half.

  • Border irregularity. The edges of the mole are ragged or irregular.

  • Color. The mole has different colors in it. It may be tan, brown, black, red, or other colors. Or it may have areas that appear to have lost color.

  • Diameter. The mole is bigger than 6 millimeters across, about the size of a pencil eraser. But some melanomas can be smaller.

  • Evolving. A mole changes in size, shape, or color.

Your health care provider will ask you about the mole. Tell him or her:

  • When you first noticed it

  • If it hurts or itches

  • If it oozes fluid or bleeds, or gets crusty

  • If it’s changed in size, color, or shape

Make sure to tell your health care provider if you’ve had skin cancer in the past. Also note whether anyone in your family has had skin cancer.

Getting a biopsy

A biopsy is a sample of tissue that’s taken to be checked in a lab. Your health care provider will likely take a biopsy of any mole or other skin mark that may look like cancer.

Types of biopsies

The different types of biopsies include the following:

  • Excisional biopsy. This type of biopsy is often used when a wider or deeper piece of the skin is needed. It’s done when a melanoma is suspected. The entire mole and part of the surrounding skin is removed. First, a local anesthetic is used to numb the area. Using a surgical knife (scalpel), a full thickness wedge of skin is removed. The wound is closed with surgical thread (sutures), staples, steri-strips, or surgical glue. This depends on the size and location of the incision.

  • Incisional biopsy. This procedure is the same as an excisional biopsy. But only part of the mole or mark is removed.

  • Punch biopsy. This type uses a special tool to take a deep sample of skin. The tool removes a short cylinder of tissue, like an apple core. First, a local anesthetic is used to numb 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 subcutis (fat). The biopsy sample is removed and the edges of the wound are then stitched together. 

  • Shave biopsy. This type of biopsy removes the top layers of skin. They are shaved off with a scalpel. Shave biopsies are done with a local anesthetic. This method may be used on a mole if the chance if melanoma is very low. This method is not usually used if melanoma is suspected.

Lab tests of your biopsy sample

A biopsy sample is sent to a lab, where a doctor called a pathologist looks at them under a microscope. He or she may do other tests on them to see if they contain melanoma cells.

If melanoma is found, the pathologist will look at certain features of the melanoma. These include the thickness of the melanoma and the portion of cells that are actively dividing (mitotic rate). These can help determine the extent (stage) of the melanoma. The stage of melanoma helps determine treatment options.

The pathologist might also do other tests to look for certain gene changes within the melanoma cells that could affect treatment options. For example, about half of all melanomas have changes in the BRAF gene that help the cells grow. Certain medicines can help treat melanomas that have this change. But these medicines are not likely to help treat melanomas without this gene change. Testing the cells before treatment is important.

Getting your biopsy results

Your biopsy results will likely be ready in a few days to a week or so. Your health care provider will notify you of the results. He or she will talk with you about other tests that may be needed if melanoma is found.