A biopsy is a medical test involving the removal of cells or tissues for examination. It is the removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically. When an entire lump or suspicious area is removed, the procedure is called an excisional biopsy. When only a sample of tissue is removed with preservation of the histological architecture of the tissue’s cells, the procedure is called an incisional biopsy or core biopsy.
Multiple methods for skin biopsy exist. Each has its own limitation and problems. Most are done under local anesthesia in a doctor’s office.
This is done with either a small scalpel blade, a curved razor blade, or a broken piece of “safety” razor. The technique is very much user skill dependent, as some surgeons can remove a small fragment of skin with minimal blemish using any one of the above tools, while other have great difficulty securing the devices. Ideally, the razor will shave only a small fragment of protruding tumor and leaving the skin relatively flat after the procedure. Hemostasis is obtained using light electrocautery.
This is done with a round shaped knife ranging in size from 1 mm to 8 mm. The common punch size use to diagnose most inflammatory skin condition is the 3.5 or 4 mm punch. Ideally, the punch biopsy include the full thickness skin and subcutanous fat in the diagnosis of skin diseases. One or two sutures are required to close most punch biopsies with the exception of the smallest punches.
Incisional biopsy is done with a scalpel. Incisional biopsy often yield better diagnosis for deep pannicular skin diseases and more subcutanous tissue can be obtained than a punch biopsy.
The result is an elliptical defect which is closed with one or two surgical sutures.
Advantage of the incisional biopsy over the punch method is that hemostasis can be done more easily due to better visualization.
This is essentially the same as incision biopsy, except the entire lesion or tumor is included. This is the ideal method of diagnosis of small melanomas (when performed as an excision). Ideally, an entire melanoma should be submitted for diagnosis if it can be done safely and cosmetically. At this point, the clinician can be confident that an excisional biopsy can be performed without risking committing a “false positive” clinical diagnosis.
Fine needle aspirate
This is done with the rapid stabbing motion of the hand guiding a needle tipped syringe and the rapid sucking motion applied to the syringe. It is a method used to diagnose tumor deep in the skin or lymphnodes under the skin. Fine needle aspirate can be used to distinguish a cystic lesion from a lipoma.