TYPES OF BIOPSIES

[drmithila]

tYPES OF bIOPSY
Depending on the characteristics of the target lesion, the
biopsy is defined as direct (located superficially, with easy
access) or indirect (when the lesion lies in depth and is covered by normally appearing mucosa or tissue)(3). However,
biopsies can also be classified according to the technique
used, the material employed, the clinical timing, the location of the target lesion, processing of the sample, and the
purpose of the biopsy.
1) The technique employed:
Depending on the technique employed, biopsies can be classified as incisional or excisional. The incisional technique
involves the removal of a representative portion of the target
lesion and of a part of healthy tissue (3,7,8). If the lesion is
extensive, different samples should be obtained, placing each
of them in a separate and adequately identified container.
Along with the report sent to the pathologist, a schematic
representation of the lesions should be attached, specifying the original location of each sample (1,3,9). Such an
approach is indicated in the case of suspected malignancy
or precancerous lesions. Likewise, such a multiple sample
biopsy should be performed when the target lesion is difficult
to remove due to its large size or complicated location. It is
also indicated for establishing the diagnosis of a systemic
disease process.
Controversy exists as to the possibility that incisional biopsies of malignant lesions may increase the risk of metastasis,
by disrupting the barrier preventing migration of the neoplastic cells and thus favoring invasion of the bloodstream
at the site of the surgical wound (10).
In certain tumors such as hemangioma or melanoma, the
biopsy should be performed with complete and extensive
resection of the lesion, in order to avoid severe bleeding or
metastatic spread, respectively (9).
An excisional biopsy in turn involves total removal of the
lesion, with slight peripheral and in-depth safety margins,
applicable to papillomas, fibromas or granulomas (4,11).
Such biopsies play a diagnostic and therapeutic role, since
complete removal of the lesion is carried out, ensuring inclusion of periphery of normal tissue

        

[drmithila]

A number of cutting instruments can be used when performing a biopsy: a conventional scalpel, a punch, and the
so-called B-forceps. Electroscalpels and CO2 laser scalpels
deserve separate mention, for although they are used by
some authors, their associated inconveniences make them
scantly recommendable for obtaining a biopsy sample.
The oral mucosal punch is a rapid, simple, safe and inexpensive technique for obtaining a representative sample of
most oral zones. The technique and usefulness are similar
to those of the skin punch. The instrument consists of a
sterile and discardable punch with a plastic handpiece and
cylindrical cutting blade. The latter may be 2, 3, 4, 5, or 6 to
8 mm in diameter, with stepwise increments of 0.25 a 0.50
mm. As a result, tissue cylinders 2 to 8 mm in diameter can
be obtained – the most widely used caliber being 4 mm.E506
Med Oral Patol Oral Cir Bucal. 2007 Nov 1;12(7):E504-10. Oral biopsy
The punch is grasped between the index and thumb, supporting the cylinder over the target lesion. If a small-diameter cylinder is obtained, suturing of the residual wound is
usually not necessary, and the bleeding can be contained by
simply applying a piece of gauze or surgical dressing. The
wound heals by second intention, with good esthetic results.
In other cases, primary wound closure can be performed
with sutures.
Punches are typically made of plastic or metal. The metal
presentations can be reused, and are to be sterilized before
use. In contrast, the plastic variants are less expensive, weigh
less and are destined for single use (13,14).
The punch is able to obtain several samples at the same time,
and at different points, and generates less patient anxiety
than the conventional scalpel (15).
However, the punch is unable to remove large lesions, and
cannot be used in intensely vascularized or innervated areas.
It is likewise not applicable to deep lesions, and is limited
to epithelial or superficial mesenchymal target tissues. Caution is moreover required when using the punch to sample
lesions located over important submucosal structures such
as the mental or nasopalatine foramen. On the other hand,
the instrument is difficult to use in the region of the soft
palate, maxillary tuberosity or floor of the mouth, due to
the lack of firm tissue fixation or support, and the mobility
of the target zone (13,14).
Other instruments, such as the so-called B forceps, can also
be used to obtain a biopsy. This instrument was developed
by Bermejo (16), and facilitates, simplifies and especially
homogenizes soft tissue biopsies of the oral cavity and of
the lesser salivary glands. These forceps are equipped with
two cusps – one with a window – to allow compression of
the target tissue between them. The target zone is positioned
exposed within the window, and the compressive effect of
the cusps allows us to work in an ischemic field within the
window. Compression by the forceps causes the sectioned
portion, freed from its peripheral connective tissue attachments, to propel from the window – thus allowing us to
measure the depth of the sample, with easy access to the
base in order to facilitate sectioning (16).
On the other hand, while the electroscalpel has the advantage of causing no bleeding, since it cauterizes the vessels,
its main inconvenience is the induction of thermal damage.
Although similar, the laser scalpel produces less extensive
thermal damage and less postoperative pain. However, in
the same way as the electroscalpel, it is currently not advised
for obtaining oral biopsies.
3) Clinical timing of sampling:
Depending on the clinical timing of the biopsy, the procedure can be classified as intraoperative or extraoperative.
An intraoperative biopsy allows a rapid histopathological diagnosis. The sampled material is processed without
fixation, frozen with dry ice. In this sense, freezing at a
temperature of between -40ºC and -60ºC produces a tissue consistency that allows sectioning with the microtome.
The quality of the preparation under such conditions is
less ideal, the analysis is more difficult, and the pathologist
faces only three diagnostic options: positive, negative or
doubtful (1,3,7).
However, the result can be received in the operating room
in a short period of time, thus allowing the surgeon to
continue with the operation as required. This procedure is
indicated when a malignant tumor is suspected, and surgery
can be planned according to the histological findings of the
intraoperative biopsy. However, the technique is not always
reliable, and in cases of doubt surgery is postponed until
conclusive results are obtained from the study of tissue
embedded in paraffin.
A very important procedure is the intraoperative examination of the margins of a resected malignant tumor, to evaluate the possible existence of tumor invasion beyond these
margins. In such a case, wider resection is required (12).
On the other hand, an extraoperative biopsy requires a
longer processing time. The fixed tissue sample is processed
and embedded in paraffin, followed by the cutting and staining of thin sections. These preparations offer greater quality
than frozen samples, and histopathological evaluation is
therefore easier (1,3).
4) Sampling location:
Depending on the topography involved, the biopsy can be
obtained from the oral mucosa in its different locations
(Figure 1), the salivary glands, bone, lymph nodes, and
other head and neck tissues. A biopsy of the oral mucosa is
simple to perform, and is used to distinguish among different types of lesions, in order to define adequate treatment
or conduct follow-up over time. A conventional biopsy is
usually indicated (6).
Regarding the salivary glands, it is very common and easy to
obtain a biopsy of the lesser salivary glands of the lips for
diagnosing or confirming an autoimmune condition such as
Sjögren’s syndrome (Figure 2). All the typical microscopic
characteristics of this syndrome, with the exception of the
clusters of myoepithelial cells, are usually observed in the
lesser salivary glands, and the lip glands are the most widely
used option, in view of their accessibility. Following local
anesthetic infiltration of the zone, a small incision measuring
approximately 10 mm is made in the mucosa of the lower lip;
the thickness of the sample should be sufficient to obtain
the glands without affecting the muscle layer or arteries
(1). In the case of retention cysts such as lip mucoceles, an
excisional biopsy is indicated (1,3).
On the other hand, when biopsying the greater salivary
glands, and specifically the parotid gland, fine-needle aspiration biopsies (FNAB) are increasingly used, due to their
non-invasive nature. An intraoperative biopsy is also of
interest in this context, selecting the tumor target zone and
avoiding nerve structures. However, greater salivary gland
biopsies, and particularly of the parotid gland, are rarely
performed outside the context of surgery, unless the lesion
is superficial and malignancy is suspected (6).
A bone biopsy in turn constitutes an indirect technique.
These procedures are usually more difficult, and require E507
Med Oral Patol Oral Cir Bucal. 2007 Nov 1;12(7):E504-10. Oral biopsy
16
17
Fig. 2. Biopsy of the lesser salivary glands of the lips.
Fig. 1. Lingual mucosa biopsy.
the raising of a soft tissue flap and an adequate approach
to the bone layer. After raising the mucoperiosteal flap, a
chisel and mallet are used, or the target zone is drilled to
obtain the specimen. In this sense, mention should be made
of the trephine drill, composed of a hollow cylinder with a
cutting edge, that allows the harvesting of bone cylinders of
different sizes. In the case of certain bone tumors, a piece of
trabecular bone can be collected using a curette. Bleeding
can be countered with oxidized cellulose, a gelatin sponge
or bone wax, followed by suturing of the overlying mucosal
layer. The specimen thus obtained is sent to the pathologist
together with a detailed report on the patient history, and
clinical and radiological characteristics. It is often advisable for the surgeon to see the X-rays with the pathologist
and radiologist, before establishing the definitive diagnosis.
In some cases, such as when specimen decalcification is
required, the laboratory may need more time to obtain the
results (1,3,6,17).
Lymph node biopsy is also an indirect procedure. In this
context, adenopathies are commonly the result of inflammatory or neoplastic processes. Prior clinical evaluation
and laboratory testing is required before biopsying lymph
nodes. If a biopsy is decided, then the entire lymph node
should be surgically removed.

 

        

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