CPD ACCREDITED ARTICLE
B) Tru cut biopsies
• Advantage: permits some evaluation of
architecture, are minimally invasive and multiple
samples can be obtained.
• Disadvantage: a small amount of tissue is
collected, and so only limited architecture can
be evaluated, which may lead to an incorrect
interpretation. Like looking through a porthole.
C) Punch biopsies.
•
These biopsies were designed specifically for skin
biopsies in dermatology pathology (and should
not be used for other system purpose).
D) Endoscopic and laparoscopic biopsies.
• Advantage: it is a minimally invasive procedure
to observe and sample tissues and organs
otherwise not available without open laparotomy,
thoracotomy or cystotomy. Corrective or
therapeutic surgery can be performed at the
same time.
• Disadvantage: small tissue sample size, although
larger than the other needle biopsy techniques.
Only muccousal biopsies taken, the muscular
layers are inaccessible. General anaesthesia is
required drives up the costs. There are a unique
set of issues related to specimen orientation and
induced artefacts, as a consequence of the small
size and friable nature of the samples.
E) Incisional biopsies.
• Advantage: provides a far greater amount of tissue
in the other techniques. No special tools are
required beyond scalpel and forceps. Cytology
can be performed on the same specimen. As the
sample is larger there is less likelihood of handling
artefacts which distort the tissue.
• Indications: performed when an excisional biopsy
cannot be obtained.
F) Excisional biopsies.
• Advantage: 100% of the lesion can pre-provided
for examination. Diagnosis and treatment can be
incorporated in the same procedure.
•
Contraindications: when the lesion is too large or
in an inoperable location.
Representative of the pathological process
Pathologists frequently make the fundamental error
of assuming that the biopsy they receive contains the
lesion. Neoplastic processes differ remarkably in their
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distribution through tissues and organs. Therefore,
biopsies that do not provide the entire lesion often do
not produce tissue sections that are representative of
the neoplastic process.
In uniform lesions the neoplastic process is diffused
and involves similar cells, such that sampling at any
site yields the same diagnostic tissue, as might be
observed with hepatoid adenoma or hepatoma etc.
Non-uniform lesions are punctuated or even dominated
by non-specific secondary or reactive changes which
obscure diagnostic lesions. Osteosarcoma, mammary
gland neoplasia, splenic haemangiosarcoma, soft
tissue sarcomas etc. frequently induce necrosis,
inflammation or stromal reaction scattered throughout
the lesion and in very small biopsies may not be
accompanied by the underlying neoplastic condition.
The lesion may not be present or included in the
biopsy because either it was not sampled or due to the
complication of necrosis, inflammation and reactive
tissue. Always use techniques that permit direct
visualization of the tissue being sampled (ultrasound-
guided, CT guided etc.), take multiple tissue samples,
take the interface with normal as well as areas that
look different.
Sufficiently free of artifacts
Artefacts are structures or substances not normally
present but produced by some external agent.
Artefacts which prevent interpretation are termed
fatal. The most common artefacts encountered are
related to the collection and handling of specimens
both during and immediately following the biopsy
procedure.
• Surgical crush artefact.
• Cautery artefact or thermal injury.
• Freezing artefact.
Fixation
Fixation is the singularly most important step in
producing good histopathology slides.
1. No tissue placed in formalin should ever be thicker
than 0.5-1.0 cm in thickness.
2. The amount of formalin should be at least 10 – 15
times the volume of tissue placed in it.
Large specimens such as spleens and large masses
should be bread sliced into 1 cm slices to ensure
adequate penetration of the formalin fixation. Large
pieces of tissue contain sufficient extracellular fluid
that they can dilute the formalin to substantially
less than 10%, resulting in the tissue in the jar
undergoing autolysis. Autolysis not only interferes
with diagnosis, but impairs accurate mitotic index
counts and frequently compromises tumour marker
immunohistochemistry.