A biopsy is a surgical procedure used for diagnostic purposes. It consists of cutting a small amount of tissue from the patient for examination under a microscope. In some cases, such as suspected skin cancer, the tissue can be removed directly from the suspect site. However, removal of tissue below the skin usually requires a large puncture to be made with the surgical instrument inserted into the puncture to excise a small amount of tissue from the suspect organ.
Biopsy is always an invasive procedure, and it is only considered where the diagnosis may be serious and there is no other way to confirm the diagnosis. Biopsy of certain areas, such as the brain or nerves, is extremely hazardous and is usually only considered as a last resort.