LEC MODULE 2 Flashcards
simplest, least invasive test and uses the smallest needle to simply remove cells from the area of abnormality. this is not always adequate to obtain a diagnosis, depending on the area to be biopsied
fine needle aspiration
takes out even more surrounding tissue. It takes out some of the
abnormality, but not all. The doctor will slice into the lesion and remove only a portion of it. If the lesion is found to be cancerous, further surgery may be needed to remove or excise the
entire lesion.
incisional biopsy
generally removes the entire area in question
excisional biopsy
removes not only cells, but also a small amount of the
surrounding tissue. This provides additional information to assist in the examination of the lesion.
core needle biopsy
considered the primary technique for obtaining diagnostic full-thickness skin specimens
punch biopsy
It requires basic general surgical and suture-tying skills and is easy
to learn. The technique involves the use of a circular blade that is rotated down through the epidermis and dermis, and into the subcutaneous fat, yielding a 3- to 4- mm cylindrical core of tissue sample
Punch biopsy
where small fragments of tissue are “shaved” from a surface (usually
skin).
shave biopsy
where tissue is scooped or spooned to remove tissue or growths from
body cavity such as endometrium or cervical canal
curettings
Specimens are usually received in
fixative (preservative)
Tissue specimens received in the surgical pathology
laboratory should have a __________ that lists the patient information and clinical history along with a description of the site of origin
request form
The specimens are ___________ by giving them
a number that will identify each specimen for each patient.
accesioned
Once tissues are removed from the body, their proteins and cells are digested and broken down by their own enzymes, independent of a bacterial action. This process is known as
autolysis
autolysis is retarded by _______ and accelerated at ___________
cold; room temperature
Autolysis is more severe in tissues that are rich in enzymes such as
liver, brain, and kidney
Autolysis is less rapid in
elastic and collagen tissues
Methods of tissue examination may vary according to the _______________ of the cells to be studied
structural and chemical components
a better and more effective means of studying tissues,
whether normal or abnormal, is by
examination of adequately preserved sections and
smears that are stained to demonstrate specific structures
these are usually examined when there is an immediate need for
evaluation.
fresh tissues
the use of fresh tissue examination is limited because
tissues examined in the fresh state are not permanent, and therefore, are liable to develop the changes that have usually been observed after death
advantage of fresh tissue examination
allows protoplasmic activities such as motion, mitosis, and phagocytosis to be observed
This can cause distortion of tissue due to ice crystal artifacts
slow freezing
commonly used methods for freezing include
- Liquid nitrogen
- Isopentane cooled by liquid nitrogen
- Carbon dioxide gas
- Aerosol sprays
For histochemical evaluation involving enzyme studies, tissue needs to be
- chemically active
- the important chemical constituents should not have been removed, altered or displaced
histochemical evaluation requires rapid preservation of tissue block by
freezing or quenching
aim of freezing or quenching
to produce instant cessation of cellular activity thereby preventing chemical alteration of tissue and displacement of cellular tissue components
What are the methods to be used if chemical fixation of tissue blocks is to be avoided
- freeze-drying
- freeze substitution
Solid structures and tissues must be preserved and carefully processed in the following order:
- Fixation
- Decalcification (optional)
- Dehydration
- Clearing
- Infiltration (Impregnation)
- Embedding
- Trimming
- Section-cutting (Microtomy)
- Staining
- Mounting
- Labelling
the art and science performed by the histotechnologist
histotechnology
aim of histotechnology
to produce a tissue section of good quality that will enable the pathologist to diagnose the presence or absence of disease
The first and most critical step in histotechnology
fixation or preservation of fresh tissues for examination
the process that preserves tissues from decay, thereby preventing autolysis or putrefaction
fixation
primary aim of fixation
to preserve the morphologic and chemical integrity of
the cell in as life-like manner as possible
fixation prevents
- degeneration
- decomposition
- putrefaction
- distortion of tissues
secondary goal of fixation
to harden and protect the tissue from the trauma of further handling
this alternative method (when chemical fixation is to be avoided) is mainly used in histochemistry
freeze-drying
this alternative method (when chemical fixation is to be avoided) is useful for studying soluble materials and small molecules
freeze-substitution
in freeze-substitution tissues are
cut into thin section
in freeze-substitution tissues are immersed in
liquid nitrogen
in freeze-substitution water is removed in a vacuum chamber at
-40C
Basic mechanisms of chemical fixative
- No additive Fixation
- Additive fixatives
principle of no additive fixation
alter tissues composition and stabilizes the tissue by removing the bound water attached to h-bonds within the protein molecule
fixatives used in no additive fixation
coagulant/ precipitating/ denaturing fixatives
aldehydes are
additive fixatives
additive fixatives are also known as
Cross-linking fixatives
additive fixatives form
chemical bonds between molecules of the tissue
the procedure whereby calcium or lime salts are removed from
tissues following fixation
decalcification
Decalcification should be done after _________ and before _________
fixation; impregnation
three main types of decalcifying agents
- based on strong mineral acids
- based on weaker organic acids
- composed of chelating agents.
poorly fixed tissue become
-macerated during decalcification
