Why Is A Biopsy Needed?

Reviewed by: HU Medical Review Board | Last reviewed: July 2016. | Last updated: September 2023

Healthcare providers are often able to diagnose a patient with psoriasis after carrying out a physical examination and taking the patient’s medical history. However, in some cases, the healthcare provider may need to take a skin biopsy in order to make sure that the symptoms are due to psoriasis and not some other cause1.

What is a biopsy?

During a skin biopsy, the healthcare provider takes a very small sample from an affected area of skin. The sample is sent to a laboratory, where a specialist called a pathologist examines it under a microscope to help make the diagnosis2.

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

Your healthcare provider may need to take a biopsy in order to rule out other causes of your symptoms. Other conditions that cause symptoms that may be similar to psoriasis include3:

  • Eczema (also called atopic dermatitis)
  • Ringworm (also called tinea corporis)
  • Pityriasis rosea, a type of skin rash
  • Seborrheic dermatitis, which is related to dandruff
  • Pityriasis rubra pilaris, a very rare skin condition

Some people develop symptoms that look like psoriasis after taking certain types of medications4. A biopsy can help to find out if this is the cause of the symptoms, which usually clear up after the person stops taking the medication5.

What happens when a healthcare provider performs a skin biopsy?

A skin biopsy can usually be taken in a healthcare provider’s office. First, the healthcare provider will numb the area of skin where the sample will be taken using a local anesthetic. The anesthetic is injected using a thin needle, and it can cause a brief burning or stinging feeling before the area becomes numb. Due to the anesthetic, you will not feel any pain while the sample is being taken6.

Two types of biopsies that may be used to diagnose psoriasis are called a shave biopsy and a punch biopsy. Both procedures can be performed quickly, usually within 15 minutes or so7. Results of the biopsy will generally be available within a week or so.

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During a shave biopsy, a thin sliver of skin is shaved off using a very sharp blade. This type does not usually require stitches, but does cause some bleeding. After taking the sample, the healthcare provider will apply pressure to the area, sometimes will topical medicine, and then applies a dressing7. The dressing will usually be left in place for a day or so. The scab will usually heal completely within a couple of weeks, leaving a small scar.

A punch biopsy is used to take a small, cylinder-shaped core sample that allows the pathologist to examine all of the layers of the skin. Healthcare providers use a special tool called a biopsy punch with a very small, round blade (usually between 3-4 millimeters in diameter)6. The tool is held to the skin and the healthcare provider rotates it quickly to take the sample. Sometimes this type of biopsy will require a stitch, but not always. The healthcare provider will then apply a dressing to the wound, which will also usually heal completely within a couple of weeks.

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