dr/ Nessrin G. AL- Abdallat
Histotechnology Lectures
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Histotechnology
BY
Dr/ Nessrin G. AL-Abdallat
Assistant Professor of medical laboratories
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Histotechnology Lectures
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Chapter I:
Introduction
WHAT IS HISTOTECHNOLOGY?
 Histotechnology centers on the detection of tissue abnormalities and the treatment
for the diseases causing the abnormalities.
 Dyes and chemicals are used in Histotechnology. It is important to know their
composition, how they act, and how they react with each other.
 With this knowledge, combined with an
understanding of tissue composition, the
histotechnologist treats the tissue with
these chemicals and dyes.
 The chemical reactions produce colors,
which make it possible to distinguish
tissue structures.
 In the modern histotechnology
lab
immunological and molecular (DNA)
techniques are frequently utilized to
provide accurate tumor identification
which will aid the clinician in selecting a
mode of therapy that offers that greatest
probability of cure.
Who are Histotechnologists
 Histotechnicians
(HTs)
and
histotechnologists (HTLs) are members
of a laboratory team who employ
histologic
technology
to diagnose
diseases, to conduct research, or to
instruct others in the science.
 Histotechnologists play a fundamental
role in the allied health profession. A
histotechnologist will prepare very thin
slices of human, animal or plant tissue
for microscopic examination.
 This is an important part of the intricate process of scientific investigation used in
establishing and confirming patient diagnosis. Because of the histotechnologist‘s
skillful application of sophisticated laboratory techniques, the seemingly invisible
world of tissue structure becomes visible under a microscope.
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Histotechnology Lectures
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 The tasks performed by the histotechnologist require patience, mechanical ability,
knowledge of biology, immunology, molecular biology, anatomy and chemistry.
What Histotechnicians Do?
 The histotechnician works with delicate instruments and automated equipment as
well as knives, chemicals and glass slides.
 He or she must value precision and have good hand-eye coordination and manual
dexterity.
Job opportunities
 Today, there are more jobs for histotechnicians than educated people to fill those
jobs. The future long-term employment looks bright. The need is great everywhere
throughout the country.
 Histotechnicians have an unlimited choice of practice settings. Job openings for
qualified histotechnicians can be found in:
1.
2.
3.
4.
5.
6.
7.
8.
hospitals
clinics
dermatopathology labs
public health facilities
industrial research
veterinary pathology
marine biology
Forensic pathology.
Certification
 To be sure that laboratory workers are competent and able to perform high quality
laboratory tests, the American Society for Clinical
Pathology Board of Certification (BOC) gives two
national certification exams for histology, the
histotechnician (HT) and histotechnologist (HTL).
 The histotechnologist
performs more complex
techniques
such
as
enzyme
histochemistry,
immunohistochemistry and electron microscopy.
 A histotechnologist can also teach, be a supervisor in
a laboratory or be the director of a school for
histotechnology.
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Histotechnology Lectures
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 Certification is not required to work in histology but in the highly competitive
market it is strongly encouraged.
It requires five basic steps, each an integral part of the
histotechnologist‘s job.
1- Grossing & Fixation –
 Tissue specimens taken from routine surgical cases, autopsies, or other scientific
investigations are examined, described and trimmed to proper size. This process is
referred to as “grossing the specimen”.
 The resulting specimens are preserved by placing them
in solutions designed to prevent decomposition. This is
known as fixation.
 Fixatives and Preservatives are used to preserve the
tissue, the structures of the cell, and the cell organelles
found in the individual cells (e.g., nucleus, rough
endoplasmic reticulum,and mitochondria).
 The tissues are mechanically and biochemically
stabilized in a fixative.
 The most common fixative is neutral buffered formalin (10% formaldehyde in
Phosphate buffered saline (PBS).
 It is important to consider that a fixative should not be too toxic to its handler, and
it should not damage the tissue being preserved.
2- Processing –
 water is removed from the tissue and replaced by melted paraffin wax.
 The samples are immersed in multiple baths of progressively more concentrated
ethanol (30%, 50%, 70%, 90% & 100% alcohol) to dehydrate the tissue, followed
by a clearing agent, such as xylene or Histoclear, and finally hot molten paraffin
wax (impregnation).
 During this 12- to 16-hour process, paraffin wax replaces the xylene.
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i3- Embedding –
 Before the wax permeated tissue can be cut it is placed
in a larger wax block for additional holding support
during sectioning.
 Soft, moist tissues are turned into a hard paraffin
block, which is then placed in a mold containing more
molten wax (embedded) and allowed to cool and
harden.
 Embedding can also be accomplished using frozen,
non-fixed tissue in a freezing medium.
 This freezing medium is liquid at room temperature but when cooled will solidify.
4- Sectioning –
 The tissue is mounted onto a delicate instrument called
a microtome. An extremely sharp knife is used to cut
sections of the tissue embedded in the wax block.
 These sections are cut one after another to form a
ribbon, which is floated on warm water to soften and
flatten tissue sections. These sections are then placed on
microscopic slides and stored for future procedures.
 The tissue is then sectioned into very thin (2–8
micrometer) sections using a microtome.
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Histotechnology Lectures
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