Many medical conditions, including all cases of cancer, must be diagnosed by removing a sample of tissue from the patient and sending it to a pathologist for examination. This procedure is called a biopsy and involves a microscopic examination of the tissue sample.
Biopsied specimens are obtained by a doctor and sent for examination to a pathologist, who prepares a report with information designed to help the primary doctor manage the patient’s condition properly.
Although most biopsies are performed on unhealthy tissue for diagnosis of a disease, healthy tissue can be obtained for matching tissue-type for transplants.
Types of Biopsies
Shave biopsy: the outer part of the suspect skin area is removed. A local anesthetic is injected. Then a scalpel is used to cut off a growth protruding from the normal tissue.
Punch biopsy: a small cylinder of tissue is removed. A local anesthetic is injected. The skin around the biopsy site is pulled tight and a punch (a hollow instrument) is firmly introduced into the skin and rotated to obtain a sample; then the punch is removed. If a large sample is taken, the area may be closed with stitches.
Excision biopsy: the entire suspect area, organ or lump, is removed. Some types of tumors have to be examined whole to allow an accurate diagnosis. Excisional biopsies of most breast lumps are preferred to ensure diagnostic accuracy. A local anesthetic is injected. Then the entire lump, spot, or sore is removed, going as deep as necessary to get the entire area. The incision is then closed with stitches.
Incisional biopsy: a part of the suspicious area is removed. This type of biopsy is most commonly used for tumors of the soft tissues (muscle, fat, connective tissue) to distinguish benign conditions from malignant soft tissue tumors, called sarcomas.
Endoscopic biopsy: the most commonly performed type of biopsy of internal tissues. It is done through a fiberoptic endoscope the doctor inserts into the gastrointestinal tract, urinary bladder, abdominal cavity, joint cavity, mid-portion of the chest, or trachea and bronchial system, either through a natural body orifice or a small surgical incision. The endoscopist can directly visualize an abnormal area on the lining of the organ in question and pinch off tiny bits of tissue with forceps attached to a long cable that runs inside the endoscope.
Colposcopic biopsy: a gynecologic procedure generally used to evaluate a patient who has had an abnormal Pap smear. The colposcope is actually a close-focusing telescope that allows the physician to see in detail abnormal areas on the cervix of the uterus, so that a good representation of the abnormal area can be removed.
Fine needle aspiration: an extremely simple technique in which a needle no wider than that typically used to give routine injections is inserted into a tumor, and a few tens to thousands of cells are drawn up into a syringe. A diagnosis can often be rendered in a few minutes. Tumors of deep, hard-to-get-to structures (pancreas, lung, and liver, for instance) are especially good candidates for FNA, as the only other way to sample them is with major surgery. Such FNA procedures are typically done by a radiologist under guidance by ultrasound or computed tomography (CT scan) and require no anesthesia, not even local anesthesia. Thyroid lumps are also excellent candidates for FNA.
Bone marrow biopsy: In cases of abnormal blood counts, such as unexplained anemia, high white cell count, and low platelet count, it is necessary to examine the cells of the bone marrow. The skin over the biopsy site is deadened with a local anesthetic. A needle is inserted to deaden the surface membrane covering the bone. A large, rigid needle is then introduced into the marrow space and marrow cells are then drawn into the syringe. This is followed by a core biopsy, in which a slightly larger needle is used to extract a core of bone.
Skin Biopsy
Skin biopsies are performed to identify cancers and benign growths, to help diagnose chronic bacterial and fungal skin infections, and to identify other skin conditions.
When skin cancer is suspected some common biopsy interpretations include:
- Normal tissue, no abnormalities
- Not normal, but not cancerous or malignant (often some type of inflammation)
- Not normal – difficult to interpret (another biopsy may be necessary for diagnosis)
- Not normal – not cancerous but a pre-cancerous condition (tissue has characteristics of cancer or malignancy)
- Cancer
Risks Involved
Risks involved with any biopsy depend on the technique and body part that is biopsied. All biopsies have the common risk of bleeding, pain, and infection. Also, anytime the skin is cut a scar will from.
In addition, there is always the risk that biopsy results may be inconclusive or difficult to interpret. If this occurs, additional biopsies may be required for a definite diagnosis.
Interpreting a Biopsy
Biopsied tissues may be prepared in many ways, often referred to as staining. Stained tissue is examined under a microscope. A pathologist studies the tissue and gives an opinion whether the tissue is normal or not.
Usually biopsy results are available within two or three days. Biopsy results that are unclear often cause delays. Sometimes, several pathologists will aid in the interpretation of a tissue sample.
A biopsy can reveal cancer but does not rule out the existence of cancer. If the tissue sample does not contain cancer cells within it, cancer may still exist somewhere else in areas not biopsied. Pre-cancerous tissue is usually monitored closely and may be treated with an anti-cancer treatment cream containing 5-fluorucacil. This cream is often as effective as surgery.
Dr. B. Wayne Blount, M.D.
Dr. Blount is the Past Professor and Chairman of the Department of Family Medicine at the University of Tennessee at Memphis School of Medicine.