Depending on the processing procedure involved, the
sample can be analyzed frozen, or embedded in paraffin
or methacrylate, and can be examined under the electron
microscope, or as a fresh sample. Molecular analyses are
also possible.
As commented above, frozen biopsies allow a rapid histopathological diagnosis. This procedure is usually used
during surgery in order to allow immediate treatment
decisions to be taken. However, the technique is contraindicated in the case of very hard tissues (bone or calcified
tissue), lesions requiring more extensive study due to their
complexity, or when no immediate diagnostic decision is
required (3,6,7,12).
Embedding in paraffin is indicated for light microscopic
evaluation, and is the most commonly used technique.
The sampled tissue is fixed in 10% formaldehyde solution.
The most characteristic zones are selected from among the
excess tissue resected. The specimen is processed by means
of an automatized, serial hot paraffin embedding system
involving progressive dehydration and final cooling and
solidification, before sectioning with the microtome. The
embedding process takes about 24 hours. Microtome sectioning is then carried out, mounting the specimens on slides
and posteriorly removing the paraffin, with rehydration and
staining as required. Finally, the specimen is again dehydrated and sealed with a coverslip. The staining techniques
used depend on the type of histological study made (1).
On the other hand, embedding in methacrylate is used for
electron microscopic studies, and when hard tissues or materials are involved. Electron microscopy is able to reveal
a series of morphological features that distinguish normal
cells from tumor cells. It is also able to establish the extent
of the tumor (12).
Fresh specimen studies require transport of the biopsy
sample as quickly as possible to the laboratory, for immunofluorescence evaluations. The specimens are to be
humidified with saline solution to prevent drying. Before
and during transport, the tissue can be kept refrigerated
(2-8ºC), though freezing must be avoided (17).
Immunofluorescence techniques in turn are either direct or
indirect, depending on whether the test antigen is detected
with a first labeled antibody or using a second anti-antibody,
respectively (18).
In our setting, these procedures are useful for diagnosing
mucocutaneous diseases of an autoimmune nature, such as
pemphigus, pemphigoid, erythema multiforme and lichen
planus (Table 1).
In the case of molecular studies, genetic molecular markers
allow us to detect alterations before changes in cell morphology occur or clinical manifestations develop. Analysis of
such molecular alterations is objective, and aims to identify
specific genetic anomalies.E508
Med Oral Patol Oral Cir Bucal. 2007 Nov 1;12(7):E504-10. Oral biopsy
VULGAR PEMPHIGUS PEMPHIGOID
ERYTHEMA
MULTIFORME
LICHEN PLANUS
DIF
IgG 100% C3 40% IgM,
Fibrinogen
IgG (particularly)
C3 IgM IgA negative
Fibrinogen (particularly)
IgG 35%
IgM 30%
IIF Ab IgG 80-90% negative negative negative
LUPUS
ERYTHEMATOSUS
LINEAL IgA
DERMATOSIS
HERPETIFORM
DERMATITIS
EPIDERMOLYSIS
BULLOSA
DIF
IgG IgA IgM C3 C4
IgA
IgA
C3
IgG
C3
IIF negative negative negative negative
table 1. Evaluation of test positivity for diagnosis via direct / indirect immunofluorescence in application to autoimmune
mucocutaneous diseases.
DIF: Direct immunofluorescence; IIF: Indirect immunofluorescence; Ig: Immunoglobulin; C: Complement fraction
The principal oral cavity carcinogens are chemical (tobacco
smoke), physical (radiation) and infectious agents (papillomavirus, Candida); as mutagens, they are able to induce
structural changes in genes and chromosomes through point
mutations, deletions, insertion or rearrangements. However,
some changes of this kind can also occur spontaneously.
Such genetic alterations taking place in the context of
carcinogenesis can be used as targets for the detection of
tumor cells in clinical samples (6).
6) Purpose of the biopsy:
Biopsies can be performed for diagnostic or experimental
purposes. Thus, apart from diagnosis with a view to treatment, a biopsy can yield important information for the
histopathological study of new disease entities. With this
aim in mind, studies are made in laboratory animals, and
exceptionally also in humans, with the obtainment of samples that can yield valuable information on the evolution of
a given disease process
.