02 Types Of Biopsies
Description
This article is from the The Biopsy Report: A Patient's Guide, by Ed Uthman uthman@neosoft.com with numerous contributions by others.
02 Types Of Biopsies
1. Excisional biopsy. A whole organ or a whole lump is
removed (excised). These are less common now, since the
development of fine needle aspiration (see below). Some types
of tumors (such as lymphoma, a cancer of the lymphocyte blood
cells) have to be examined whole to allow an accurate
diagnosis, so enlarged lymph nodes are good candidates for
excisional biopsies. Some surgeons prefer excisional biopsies
of most breast lumps to ensure the greatest diagnostic
accuracy. Some organs, such as the spleen, are dangerous to
cut into without removing the whole organ, so excisional
biopsies are preferred for these.
A special type of excisional biopsy of the breast is the
needle localization biopsy, also called the "wire-guided
biopsy." This is used when the patient presents with an
abnormal mammogram, but no lump can be felt in the breast.
Since the surgeon cannot feel anything, it is necessary for
the radiologist, who can see the abnormality on the x-ray, to
provide some sort of guide. While the patient is positioned
in the mammography machine, the radiologist (a physician who
specializes in diagnostic imaging) uses the mammogram and a
special grid to insert a needle directly into the abnormal
area. When a follow-up mammogram determines the needle is in
the right place, a wire with a barb on the end is inserted
through the hollow needle into the abnormal area. The needle
is withdrawn from around the wire, leaving the wire fixed in
place (because of the barb, it cannot fall out). The surgeon
then cuts into the breast and follows the wire to the area in
question, removes this area, and sends it to the pathologist.
The pathologist then determines if the appropriate tissue has
been removed and advises the surgeon appropriately. In some
cases, it is necessary to x-ray the actual biopsy specimen to
determine if the suspicious area has been removed.
2. Incisional biopsy. Only a portion of the lump is removed
surgically. 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.
3. Endoscopic biopsy.This is probably the most commonly
performed type of biopsy. It is done through a fiberoptic
endoscope the doctor inserts into the gastrointestinal tract
(alimentary tract endoscopy), urinary bladder (cystoscopy),
abdominal cavity (laparoscopy), joint cavity (arthroscopy),
mid-portion of the chest (mediastinoscopy), or trachea and
bronchial system (laryngoscopy and bronchoscopy), 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.
4. Colposcopic biopsy.This is a gynecologic procedure that
typically is 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 and sent
to the pathologist.
5. Fine needle aspiration (FNA) biopsy.This is an
extremely simple technique that has been used in Sweden for
decades but has only been developed widely in the US over the
last ten years. A needle no wider than that typically used to
give routine injections (22 to 25 gauge) is inserted into a
lump (tumor), and a few tens to thousands of cells are drawn
up (aspirated) into a syringe. These are smeared on a slide,
stained, and examined under a microscope by the pathologist.
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.
Because of recent interest in cost containment, FNA is now
widely applied in diagnosing breast lumps. While the
technique is excellent in experienced hands, false negatives
and false positives do occur. A false negative causes delay
in diagnosis of breast cancer allowing the tumor to grow and
spread, and a false positive is likely to result in an
unnecessary mastectomy. I would therefore offer the following
recommendations to any patient who has been encouraged to
have a breast FNA:
Studies have clearly shown that the diagnostic accuracy
of breast FNA is optimal when the same person who
interprets the smears also performs the biopsy itself.
Accordingly, I recommend that patients have the actual
procedure performed by a pathologist who does a good
number of these cases as a part of his or her practice.
FNAs that are positive for cancer should be confirmed
by frozen section at the time of surgery, before the
mastectomy is performed.
An FNA that shows no cancer cells is no assurance that
the patient does not have cancer. A negative FNA means
that either 1) the patient does not have cancer, or 2)
the patient does have cancer, but the needle missed the
diagnostic cells.
6. Stereotactic needle biopsy. This relatively new technique
for evaluating breast lesions attempts to combine the
advantages of FNA (no scar, no anesthesia, inexpensive),
excisional biopsy (acquisition of solid pieces of tissue
rather than smears) and needle localization (precise guidance
by x-ray or ultrasound imaging). The patient lies on her
abdomen, so that the breast hangs down into a space that can
be x-rayed by a computerized imaging device. The computer
displays the mammographic image on a screen. The radiologist
identifies the abnormality and marks it electronically on the
screen. The computer then positions a movable arm directly
over the abnormal area. A biopsy device is attached to the
arm, and the spring-loaded gun quickly inserts a hollow
biopsy needle into the breast. The needle is removed, and the
tissue it contains is sent to the pathologist for diagnosis.
The downside of stereotactic needle biopsy is that, because
only a tiny amount of tissue is removed, a negative result is
no guarantee the patient does not have cancer. Another
problem is that occasionally the biopsy will remove the
portions of the lesion that were responsible for its being
identified as abnormal in the first place. This leaves the
surgeon with no "signpost" to follow in trying to remove by
lumpectomy a cancer that was diagnosed by stereotactic needle
biopsy.
7. Punch biopsy. This technique is typically used by
dermatologists to sample skin rashes and small masses. After
a local anesthetic is injected, a biopsy punch, which is
basically a small (3 or 4 mm in diameter) version of a cookie
cutter, is used to cut out a cylindrical piece of skin. The
hole is typically closed with a suture and heals with minimal
scarring.
8. 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. In adults, the sample is usually taken from the
pelvic bone, typically from the posterior superior iliac
spine. This is the prominence of bone on either side of the
pelvis underlying the "bikini dimples" on the lower
back/upper buttocks. Hematologists do bone marrow biopsies
all the time, but most internists and pathologists and many
family practitioners are also trained to perform this
procedure.
With the patient lying on his/her stomach, the skin over the
biopsy site is deadened with a local anesthetic. The needle
is then inserted deeper to deaden the surface membrane
covering the bone (the periosteum). A larger rigid needle
with a very sharp point is then introduced into the marrow
space. A syringe is attached to the needle and suction is
applied. The marrow cells are then drawn into the syringe.
This suction step is occasionally uncomfortable, since it is
impossible to deaden the inside of the bone. The contents of
the syringe, which to the naked eye looks like blood with
tiny chunks of fat floating around in it, is dropped onto a
glass slide and smeared out. After staining, the cells are
visible to the examining pathologist or hematologist.
This part of procedure, the aspiration, is usually followed
by the core biopsy, in which a slightly larger needle is used
to extract core of bone. The calcium is removed from the bone
to make it soft, the tissue is processed (see "Specimen
Processing," below) and tissue sections are made. Even though
the core biopsy procedure involves a bigger needle, it is
usually less painful than the aspiration.
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