BIOPSY

[Drsumitra]

HOW tO PERFORM AN ORAL bIOPSY
The materials and instrumentation required to perform an
oral biopsy are not particularly sophisticated. The necessary
instruments are limited to those commonly employed in
surgery, such as a buccal mirror, exploratory probe, toothless
dissection forceps, mosquito forceps, scalpel handpiece and
number 15 blade, syringe for anesthesia, pressure forceps,
scissors, periostotome, separators, needle carriers and suture mounted needles. For bone biopsies we can use gubia
forceps, a chisel and mallet, a motor-driven handpiece with
drills, and curettes.
As to the required material, an ejector, gauze, sterile gloves
and a plastic or glass bottle containing 10% formalin solution is advised (3).
As with any surgical procedure, a biopsy requires due
sterilization of the instrumentation and disinfection of the
surgical field.
Most target lesions are found in soft tissues such as the
tongue, cheek mucosa or lips, or in more adhered regions
such as the palate and gums. Anaesthesia with a vasoconstrictor to minimize bleeding should not be applied in the
actual biopsy target zone but rather at a certain distance, to
avoid alterations. Thus, injection should be performed with
a separation of 3-4 mm, and at the four cardinal reference
points (top, bottom, left and right).
The specimen should be obtained by means of a clean
and deep cut, taking care in extraction to avoid tearing or
compression, as this could cause alterations. In excisional
biopsies, the lesion is to be palpated carefully, determining
its depth, and the incisions should slightly exceed the total
depth of the lesion. In incisional biopsies, any depth within
the lesion allowing the obtainment of sufficient material for
study is considered acceptable. The incision should include a
significant portion of the suspect tissue, though also a part
of adjacent normal tissue (19).
The wound margins are subjected to debridement, with
control of bleeding, and the lips of the wound are joined
with suture. When a sample of gingival tissue or palate is
obtained, and closure of the incision proves difficult, it can
be left to heal by second intention. Oxidized and regenerated
cellulose can be applied, together with gauze impregnated
with tranexamic acid, to avoid bleeding (8).
After obtaining the sample, washing with physiological
saline is indicated, followed by fixation. Sample processing begins once the specimen has been obtained, with the
purpose of allowing tissue study under magnification. The
steps comprise fixation, cutting into fragments or blocks,
embedding, sectioning, staining and examination. The most
common procedure is staining with hematoxylin-eosin, followed by examination under the light microscope (1).
Light microscopic studies generally involve the use of 10%
formaldehyde solution in water; the concentration must be
sufficient to ensure correct fixation of the tissue.
If prolonged storage of the specimens is contemplated, we
can use Bouin fixating medium, which remains stable over
time. The tissue sample is to be left in the fixating solution
for 2-10 hours, depending on its thickness. It is then washed
for 24 hours and finally immersed in 80º alcohol for posterior dehydration, clearance or embedding. The formula
for preparing Bouin medium is as follows: 1.4% picric acid
aqueous solution (150 ml), commercial formalin solution
(50 ml) and glacial acetic acid (19 ml)(3).
Other simple fixing fluids can also be used, such as picric acid,
acetic acid, chromic acid, potassium dichromate, mercury
chloride, cadmium chloride, osmium tetraoxide (osmic acid),
acetone or 70% alcohol – though the latter sharply dehydrates
the tissues, causing artifacts, complicating epithelial staining
and poorly fixing the connective tissue elements (3).
On the other hand, for electron microscopic preparations,
the specimen is immersed in 3% glutaraldehyde in the refrigerator for 24 hours, followed by transfer to a 0.1 M buffer
solution until study (3).
Oral cavity biopsies can give rise to complications, though in
most cases such problems can be minimized by making use
of a careful surgical technique. Bleeding may occur in the
first 24 hours after the procedure, as a result of clot disruption during the early healing period, or secondary to suture
loosening. Minor bleeding responds to local pressure application, while more important bleeding requires ligation,
cauterization or the closure of some bleeding point (11).
Dehiscences are infrequent, however. Such problems may
develop 5-8 days after biopsy. The implicated local factors comprise bleeding, infection, excess suture material
or excessively tightened sutures that tend to strangle local
vascularization (11).
On the other hand, infection is also rare and is attributable
to a deficient surgical technique. Treatment in such situations consists of drainage of the infectious material, and
antibiotic medication.
Another possible complication of oral biopsies is sensory
impairment. This type of problem may result from a defective surgical technique, and can be avoided. Sensory defects
are secondary to sensory nerve damage during the biopsy
procedure. The symptoms are paresthesia of variable intensity that can persist for hours or even several months,
depending on the magnitude of the damage caused (11).
The pathologist must be duly informed of the identifying
data of the biopsied lesion, i.e., its macroscopic appearance,
and the zone in which it is located.
The specimens obtained with oral biopsy procedures are
typically small, and the risk of artifacts is considerable.
These artifacts, which are sometimes seen under the microscope, may pose a problem for establishing a correct
histopathological diagnosis.
Biopsy artifacts are due to defective sampling techniques,
problems during transport, or incorrect processing of the
tissue in the laboratory.
A small sample usually consists of a narrow strip of delicate
mucosa, which tends to fold onto itself during fixation.
When this happens, the junction between the epithelial and
connective tissue components is usually lost – particularly
if the specimen lacks an underlying submucosal or muscle
tissue layer.
On one hand, when the tissue is removed with excessive
force, the epithelium and connective component may suffer
important damage. The forceps used to grasp the specimen
may perforate the latter, leaving gaps and creating compression zones around the tissue (20-22).
On the other hand, the heat generated by an electroscalpel
gives rise to alterations such as tissue protein coagulation
– resulting in an amorphous epithelial and connective tissue
appearance. In such situations the epithelial cells become
fusiform and hyperchromatic (18,21). Some authors recommend combination of an electroscalpel and conventional
scalpel. The technique in this case consists of application of
the conventional scalpel for incision around the target lesion,
with use of the electroscalpel to complete tissue removal.
This approach affords increased hemostasia and reduces
the amount of heat generated. However, the electroscalpel
is generally not advised, and when it is used, a marginal
incision should be made at a good distance from the tissue
sampling zone, in order to avoid heat-induced changes in
the target area.