Skin Biopsy

Why It Is Done

A skin biopsy is done to diagnose a:

• Skin condition (if it is not already clear what the condition is), such as psoriasis.
• Disease, such as skin cancer.
• Bacterial or fungal skin infection.

How To Prepare

Before a skin biopsy, tell your doctor if you:

• Are taking any medicines, particularly anti-inflammatory medicines such as prednisone. Anti-inflammatory medicines may change the way your biopsy looks under the microscope.
• Are allergic to any medicines.
• Take a blood thinner, or if you have had bleeding problems.
• Are or might be pregnant.

No special preparation is needed before having this test.

You may be asked to sign a consent form that says you understand the risks of the test and agree to have it done.

Talk to your doctor about any concerns you have regarding the need for the test, its risk, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form (What is a PDF document?).

How It Is Done

Usually the place where the biopsy will be taken is cleaned with an alcohol wipe. A marker may be used to outline the edges of the skin sample. For some biopsies, a surgical drape is used to cover the area around the biopsy and the doctor will wear a mask, gown, and gloves.

Several different methods may be used to obtain a skin sample, depending on the size and location of the skin lesion. The skin sample is placed in a solution, such as formaldehyde, or in a sterile container if infection is suspected. In each of these procedures, the tissue is then examined under a microscope.

• Shave biopsy. After a local anesthetic is injected, a surgical knife (scalpel) is used to shave off the growth. Stitches are not needed. Any bleeding can usually be controlled with a chemical that stops bleeding and by applying pressure. The biopsy site is then covered with a bandage or sterile dressing.
• Punch biopsy. After a local anesthetic is injected, a small, sharp tool that looks like a cookie cutter (punch) is placed over the lesion, pushed down, and slowly rotated to remove a circular piece of skin. The skin sample is lifted up with a tool called a forceps or a needle and is cut from the tissue below. Stitches may not be needed for a small skin sample. If a large skin sample is taken, one or two stitches may be needed. Pressure is applied to the site until the bleeding stops. The wound is then covered with a bandage or sterile dressing.
• Excision. After a local anesthetic is injected, the entire lesion is removed with a scalpel. Stitches are used to close the wound. Pressure is applied to the site until the bleeding stops. The wound is then covered with a bandage or sterile dressing. If the excision is large, a skin graft may be needed.

How It Feels

You will feel brief stinging pain when the local anesthetic is injected. You should not feel any pain when the skin sample is removed.

What Affects the Test

Taking medicines, such as anti-inflammatory medicines, those used for fungal infections (antifungal medicines), and corticosteroid skin creams, can interfere with your test or the accuracy of the results.

What To Think About

• If the biopsy contains cancer cells, more surgery will be needed to remove the cancer completely.
• If the biopsy is done on your face, you may want to have it done by a doctor who specializes in surgical techniques that can minimize scarring, such as a plastic surgeon or dermatologist.
• Further testing may be needed if:
  • A small biopsy does not contain enough cells to make an accurate diagnosis.
  • Cells from the abnormal area weren't included in the sample.
  • The growth or skin rash changes after the first biopsy.