A skin biopsy is a procedure in which a portion of skin is removed from a patient and examined under a microscope. Also known as a skin lesion biopsy, it can help a physician to diagnose several different skin disorders.

Skin biopsies of moles, lesions or tumors are used to diagnose skin cancers or to confirm that a growth is noncancerous (benign). They may also be used to diagnose bacterial and fungal skin infections or other skin disorders. Skin biopsies are sometimes used to confirm a diagnosis of a skin disorder such as psoriasis or lichen planus.

There are several different types of skin biopsies. A number of factors help determine which type of biopsy is performed, including the size, type and location of the abnormality.

From least invasive to most invasive, they include:

• Shave biopsy. Used to biopsy more superficial skin abnormalities, it involves use of an instrument such as a scalpel to remove the very top layers of skin. It is the least invasive form of biopsy and stitches are not required to close the wound. This method may be used when benign growths or nonmelanoma skin cancer is suspected.
  
  
• Punch biopsy. Used for deeper skin abnormalities, it involves the use of a sharp, instrument resembling a cookie cutter to remove a cylinder of skin. In most cases, the sample is about the same size as a pencil eraser. When larger samples are removed, stitches may be necessary to close the wound. This method may be used to diagnose skin rashes.
  
  
• Incisional biopsy. For this type of biopsy, a local anesthetic is either injected into the abnormality or applied topically. A surgeon then makes an incision with a scalpel and part of the abnormality is removed. This method may be used when melanoma skin cancer is suspected.
  
  
• Excisional biopsy. During an excisional biopsy, the entire lump, spot or sore is removed. This type of biopsy may require a deeper incision than other types of biopsy. Once the entire abnormality has been removed, stitches are used to close the wound. A skin graft may be necessary to close the wound in an excisional biopsy where an extremely large or deep sample has been removed. This method may be used when tumors or melanoma skin cancer is suspected.

In some cases, a fluid-filled skin abnormality may be evaluated using a technique called aspiration. During this procedure, a physician uses a needle and syringe to suction out fluid from the lesion. As with the biopsies, the sample is then evaluated in a laboratory.