Why Is A Biopsy Needed?

Reviewed by: HU Medical Review Board | Last reviewed: March 2024 | Last updated: March 2024

Doctors are often able to diagnose people with psoriasis based on a physical exam and full medical history. But in some cases, the doctor may need to perform a skin biopsy. A skin biopsy can help the doctor make sure that your symptoms are due to psoriasis and not some other skin issue.1

What is a biopsy?

A biopsy is a medical procedure in which a small sample of tissue is taken from the body and then examined under a microscope. During a skin biopsy, a doctor takes a very small sample from an affected area of the skin. The biopsy is then sent to a laboratory where a specialist called a pathologist examines it under a microscope to help make the diagnosis.1,2

How can a biopsy help to make a diagnosis of psoriasis?

A biopsy can be helpful in order to rule out other skin conditions that may mimic psoriasis symptoms. These conditions include:1,2

  • Eczema (also called atopic dermatitis)
  • Cutaneous lupus, an autoimmune disorder
  • Skin infection
  • Skin cancer

By examining the skin sample under a microscope, a pathologist can identify key characteristics unique to psoriasis. These include thickened skin layers, abnormal cell growth, and inflammation. Confirming the condition is psoriasis helps your doctor provide the best treatment plan.1

The process of a skin biopsy

The process of a skin biopsy is relatively simple. It is typically performed in a dermatologist's office or outpatient clinic.2,3

First, the area of skin to be biopsied is cleaned and numbed with a local anesthetic to minimize discomfort during the procedure. Next, the biopsy is performed. There are 3 main types of biopsies used for skin conditions. For most cases of psoriasis, a shave or punch biopsy is all that is needed:2,3

Shave biopsy

With a shave biopsy, a thin sliver of skin is shaved off using a very sharp blade. This type of biopsy does not usually require stitches. But it does cause some bleeding.2

After taking the sample, the doctor will apply pressure to the area, sometimes apply a topical medicine to prevent infection, and then apply a bandage to keep the area clean and dry. The bandage will usually be left in place for a day or so. The area will scab over and usually heal completely within a couple of weeks, leaving a small scar.2,3

Punch biopsy

A punch biopsy is used to take a small, cylinder-shaped core sample. This allows the pathologist to examine deeper layers of the skin. A special skin-punch tool is used for punch biopsies. The tool has a very small, round blade at the end (about the size of a pencil eraser).2,3

A punch biopsy may require a stitch or 2, but not always. Your doctor will then apply a bandage to the wound. As with a shave biopsy, the wound from a punch biopsy will usually heal completely within a couple of weeks.2,3

Excisional biopsy

An excisional biopsy uses a scalpel to surgically remove the entire abnormal tissue or lesion. This is typically done when a larger sample is needed to make a diagnosis or when the lesion is small enough to be completely removed.2,3

Treating the area after a biopsy

After getting a skin biopsy, follow your doctor's instructions for at-home care. You will need to:3

  • Keep the biopsy site clean and dry
  • Avoid activities that may stretch the skin in the area or cause you to bump the area
  • Protect the area from sunlight and friction

Depending on the type of biopsy and the location of the biopsy, your doctor may recommend using over-the-counter pain relievers or applying topical antibiotics or bandages to help with healing and reduce discomfort.3

Keep an eye out for any signs of infection, such as drainage or increased redness, pain, or swelling. Contact your doctor if you experience any concerning symptoms.3

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Talk with your dermatologist

If you have symptoms of psoriasis, talk with a dermatologist. They can help determine the most appropriate course of action, including whether a biopsy is needed for diagnosis.

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