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

In general, there's nothing you have to do before this test, unless your doctor tells you to.

If you take aspirin or some other blood thinner, ask your doctor if you should stop taking it before your procedure. Make sure that you understand exactly what your doctor wants you to do. These medicines increase the risk of bleeding.

How It Is Done

Usually the place where the biopsy will be taken is cleaned with a special antiseptic. 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 tissue sample is then examined under a microscope.

Skin biopsy methods include:

• Shave biopsy. After a local anesthetic is injected, a surgical knife (scalpel) or special razor is used to shave off the growth. Stitches aren't 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.
• Punch biopsy. After a local anesthetic is injected, a small, sharp tool that looks like a cookie cutter (punch) is placed over the lesion. It is pushed down and slowly rotated to remove a circular piece of skin. 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 biopsy site is then covered with a bandage.
• Fine needle biopsy. A thin needle is inserted into a lump or area to remove cells, fluid, or tissue. The biopsy site is then covered with a bandage.
• 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. 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.

Risks

There is a slight risk of bleeding and infection after the biopsy. If you usually form scars after skin injuries or surgery, you could develop a scar at the biopsy site.

Results

Results from a skin biopsy usually are available in 3 to 10 days.

Normal:

• The skin sample is normal skin tissue.

Abnormal:

• Noncancerous (benign) growths are seen. (Benign growths don't contain cancer cells.) Benign skin changes include moles, skin tags, warts, seborrheic keratoses, keloids, cherry angiomas, and benign skin tumors, such as fibromas.
• Cancer cells such as basal cell cancer, squamous cell cancer, or melanoma are found.
• Diseases with skin changes, such as lupus, psoriasis, or vasculitis, are found.
• A bacterial or fungal infection is found.

Your doctor will talk with you about any abnormal results that may be related to your symptoms and past health.