Patient Basics: Skin Biopsy

Originally published by Harvard Health.

What is the test?

Doctors take biopsies of areas that look abnormal and use them to detect cancer, precancerous cells, infections, and other conditions. For some biopsies, the doctor inserts a needle into the skin and draws out a sample; in other cases, tissue is removed during a surgical procedure.

For this test, abnormal areas of skin are removed to test for cancer or other skin diseases.

How do I prepare for the test?

Tell your doctor if you have ever had an allergic reaction to the medicine lidocaine or similar types of local anesthesia.

What happens when the test is performed?

This procedure is done in a doctor’s office, often by a dermatologist. The doctor begins by injecting a local anesthetic near the biopsy site. Although the injection usually stings for a second, the rest of the procedure is painless. Depending on the size of the lesion, one of two methods will be used to remove or sample it.

For small lesions and tissue samples, your doctor might do a punch biopsy, in which he or she places an instrument shaped like a straw with a sharp end against your skin and twists it. The sharp end works like a cookie cutter to slice a small circle from the top layer of skin. The doctor lifts the tissue away with tweezers. A single stitch closes the opening in the skin.

Larger lesions and tissue samples are removed with an excisional biopsy. In this case, the doctor uses a blade to cut an oval opening around the area. The doctor will stop any bleeding with a cauterizer, a wand-shaped instrument that uses an electric current to seal the ends of bleeding blood vessels. You’ll also need stitches to close the incision.

With both types of biopsies, the skin sample is then given to a pathologist and examined under a high-powered microscope. You’ll probably be able to go home right afterward.

For skin biopsies that are being tested for melanoma, the most serious form of skin cancer, and your doctor will try to remove the entire area that looks abnormal. That way, the biopsy will not only determine if the lesion is malignant, it might also cure the cancer. The sample will be examined under a microscope to make sure the whole cancer has been removed. You might need additional skin surgery if the examination shows that the cancer extended to the margins of the skin sample.

What risks are there from the test?

If you had an excisional biopsy, you’ll have a scar shaped like a straight line. Scars are rare following a punch biopsy. There may be some minimal bleeding, and in rare cases a minor infection will develop in the skin around the biopsy. Following any kind of incision into the skin, some people develop keloids-reddish lumps on the healing skin.

Must I do anything special after the test is over?

Keep the healing wound clean and dry.

How long is it before the result of the test is known?

It can take several days to get your results.