A skin biopsy is a procedure in which a sample of skin tissue is removed, processed, and examined under a microscope.
The skin sample is placed in a solution, such as formaldehyde, or in a sterile container if infection is suspected. In each of these procedures, the tissue is processed and then examined under a microscope.
Skin biopsies most often are done to diagnose skin cancer or an inflammatory skin condition.
A punch is a round biopsy, which can take a sample of all skin layers.