Skin biopsy: what to know before, during and after

A skin biopsy is one of the most common office procedures in family medicine. It takes a small piece of a spot on the skin, or the whole spot, and sends it to a lab, where a pathologist looks at it under a microscope. Before any procedure, you should know why it's being done, what can go wrong, what else you could do and how to care for it afterward. This is the conversation I'd have with you first.

What a skin biopsy is

After numbing the skin, the doctor removes tissue in one of four ways. The choice depends on what the spot looks like, how deep the problem probably goes and where it is on your body.

Who it's for

• A spot that's changing, new, bleeding, not healing, or looks different from your other moles (the "ugly duckling").
• A mole with warning signs: asymmetry, an irregular border, several colors, a diameter over 6 mm, or any change in size, shape or color.
• A suspected skin cancer, such as a pearly bump or a scaly, crusted patch that keeps coming back.
• A rash or skin condition that isn't clear from looking at it or isn't responding to treatment.
• A bothersome growth you want removed, when it's also worth checking under the microscope.

Your risk is higher if you have a personal or family history of melanoma, fair skin, many moles or a history of bad sunburns. Living and training at altitude in Colorado means more UV exposure, so this is a common conversation here.

Who should wait, or see a specialist

• An infection or open rash at the site. It's usually better to treat that first.
• An allergy to local numbing medicine. True allergy to lidocaine is uncommon, and there are alternatives, so tell me about any reaction you've had.
• A bleeding disorder or blood thinners. Most people on aspirin or blood thinners can still have a biopsy with careful pressure and dressing, so don't stop a prescribed blood thinner on your own.
• Spots on the eyelids, nose, palms or soles, or very large lesions, are often better sent to a dermatologist or surgeon.

Benefits and risks

For perspective, a study of 5,091 skin surgeries done without preventive antibiotics found an overall infection rate of 1.47%, and 0.54% for simple excisions closed with stitches. Infections were more common below the knee and in the groin. Simple biopsies are smaller than most of those surgeries.

Alternatives

• Watch it. For a spot that looks benign, take a photo with a ruler next to it and recheck in a few months.
• Treat it without testing. Clearly benign growths like warts or seborrheic keratoses can be frozen off instead, but freezing destroys the tissue, so nothing goes to the lab.
• See a dermatologist for a second opinion, a dermatoscope exam, or a biopsy in a sensitive area.
• Do nothing. That's your right. For a suspicious spot, the risk is missing a skin cancer while it's easiest to treat.

Step by step

1. CheckWe look at the spot together, measure and photograph it, choose the type of biopsy, and you sign consent.
2. Mark and cleanThe area is outlined with a skin marker and cleaned with an antiseptic.
3. NumbLidocaine, often with epinephrine to reduce bleeding, is injected slowly with a very fine needle. Buffering it with a little sodium bicarbonate makes it sting less. After that you should feel pressure, not pain.
4. SampleShave: a thin blade slices off the spot. Punch: a round blade is twisted down through the skin and the core is lifted out. Excision: a scalpel removes an ellipse of skin around the spot.
5. Stop bleedingPressure and a medicine dabbed on the base for shaves; one or more stitches for punches and excisions.
6. DressA thin layer of petroleum jelly and a bandage.
7. LabThe sample goes to a pathologist. Results usually take several days to a couple of weeks, and you'll hear from me either way.

Aftercare

• Shave sites: keep covered and moist with petroleum jelly for at least a week. A moist wound heals with less scarring than one left to scab.
• Punch and excision sites: keep the bandage on and dry for the first 24 hours. After that, gently wash with soap and water once a day, pat dry, apply petroleum jelly and a fresh bandage.
• Plain petroleum jelly works as well as antibiotic ointment. In a randomized trial of 922 people after skin surgery, infection rates were similar (2.0% with petroleum jelly, 0.9% with bacitracin, not a significant difference), and only the bacitracin group had allergic reactions.
• Take it easy on that area for a few days. Avoid heavy lifting or stretching that pulls on stitches, and skip pools and hot tubs until the skin has closed.
• Pain is usually mild. Acetaminophen is enough for most people.

Stitches come out on a schedule that depends on where they are:

When to call

• Redness or warmth that's spreading, pus, red streaks or a fever.
• Pain that's getting worse after the second day instead of better.
• Bleeding that soaks through the bandage and doesn't stop with firm, steady pressure.
• A stitch that comes loose and the wound opens.
• You haven't heard your results when you expected to.

Which procedures Peak Health offers in the office will be confirmed before opening. You can see the full list on the Services page, and the rest of these guides in the procedure guides library.

Sources: Pickett H. Shave and punch biopsy for skin lesions. American Family Physician. 2011;84(9):995–1002. aafp.org. Dixon AJ, Dixon MP, Askew DA, Wilkinson D. Prospective study of wound infections in dermatologic surgery in the absence of prophylactic antibiotics. Dermatologic Surgery. 2006;32(6):819–826. Smack DP, Korge BP, James WD. Infection and allergy incidence in ambulatory surgery patients using white petrolatum vs bacitracin ointment: a randomized controlled trial. JAMA. 1996;276(12):972–977.