20
Fine-Needle Aspiration Biopsy Techniques
Fig. 20.1 (A) Advance the plunger of the syringe to express a small drop of the sample, approximately 2-3 mm in diameter, onto the center of a glass slide.
This may be performed over a series of slides, or using one slide at a time followed by preparing the smear. (B) Invert another plain glass slide over the drop;
as the drop spreads, the two slides are pulled apart horizontally in a single gentle motion.
latter to prevent or inhibit clotting. The author has found that
both solutions dilute the specimen and destroy cytologic pat-
terns when preparing smears.
A cyst may be encountered in aspirating a mass. This is not
an uncommon occurrence when aspirating a thyroid or breast
nodule. The cyst should be evacuated as completely as possible.
When a cyst is encountered, the author moves the needle in a
wider cone while pressing on the mass to help evacuate it as
completely as possible. It is useful to inform the patient that
a cyst has been found and that it may take a moment longer
to evacuate it, keeping in mind the patient's level of comfort
with the procedure. When a cyst is aspirated, the author with-
draws the needle with some vacuum in the syringe in an effort
to remove the last drop of fluid from the mass and collapse the
walls together using the palpating hand. Excessive pressure is not
necessary to accomplish this. The most important point when
aspirating a cyst is to re-examine the patient for any residual
mass and to
re-aspirate
any lesion that remains. This may help
to ensure that a true neoplasm is not overlooked, particularly a
metastatic tumor that has undergone cystic degeneration.
As described above, the aspiration technique for deep lesions
is the same, following the administration of local anesthesia,
through the chest or abdominal wall to the level of the pleura or
peritoneum. Anticipating that multiple aspirations will often be
made of the same mass, radiologists will place a guide needle,
usually 18-gauge, through the skin, subcutaneous tissue, and
muscle and close to the surface of the target for biopsy. The cor-
rect position of the guide needle is then checked by imaging.
The aspirating needles of 21 and 22 gauge or needles for micro-
core biopsy are then inserted through the guide needle. Modern
imaging techniques allow the actual depth of the target to be
determined quite accurately. A stop is placed on the aspiration
needle so that the depth of the mass is correctly determined.
After placement of the aspiration needle through the guide nee-
dle, its position may also be rechecked by imaging before the
actual aspiration sample is obtained. Because of the motion of
respiration may affect the correct placement of the aspirating
needle, particularly for lung lesions, the patient is asked to hold
their breath when the aspirating needle is inserted into the mass
and the sample obtained. This maneuver also reduces trauma to
the pleura, which in turn lowers the risk for pneumothorax.
Many masses aspirated by image guidance are not homo-
geneous. Sampling the middle of a necrotic tumor will not
lead to a correct or even satisfactory diagnosis. The presence of
the pathologist to immediately prepare smears and report the
non-diagnostic nature of the smears should lead to a more pre-
cise placement of the needle at the edge of a lesion to obtain
definitive diagnostic material that is better preserved. This
collaborative type of service helps significantly in obtaining
high-quality specimens and adequate samples for any ancillary
studies that need to be performed.
Developing the necessary confidence to perform FNA takes
practice. Some experience and confidence can be obtained by
the performance of aspiration biopsies on both cadavers and
surgical specimens. The mechanics of handling the syringe gun
and the several steps involved in the aspiration biopsy will
become automatic. Smear preparation, which is discussed next,
is also an important part of any practice; both to gain facility
at this important technique and to collect smears made from
normal tissues as well as neoplasms both benign and malignant
and even non-neoplastic conditions. This collection of smears
forms an excellent reference source for comparing with patient
specimens.
Smear Preparation
1.
Immediately
after completing the aspiration biopsy,
quickly remove the needle from the syringe; then pull
back on the syringe pistol to fill the syringe with air.
2. Reattach the needle; place the needle near the center
and touching the surface of a plain glass slide.
3. Advance the plunger of the syringe, which will express
a small drop of the sample, approximately 2-3 mm
in diameter, onto the slide (Fig. 20.1A).
4. Quickly continue this procedure over a series of five
to six slides.
5. Invert another plain glass slide over the drop; as it
spreads from just the weight of the slide, pull the two
slides apart horizontally in a single gentle motion
(Fig. 20.1B).
6. As an alternative, when the drop spreads in a circu-
lar fashion, again from the weight of the slide, pull
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