2. Learning Objectives
Upon completion of this chapter, the student will be able to:
1. Define cytopathology.
2. List various applications of cytopathological diagnosis.
3. Explain the diagnostic techniques used in cytopathology.
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Histopathology lecture notes
4. 7.1 Introduction to Cytology
Cytology is the scientific study of the structure and function of
cells.
Screening involves the examination of samples from
asymptomatic individuals to detect premalignant or early
malignant changes.
Diagnostic work involves the assessment of material from
patients with established signs or symptoms of disease.
It is a basic premise that the content of a cytology specimen
should accurately and reproducibly represent the cell population
of the target tissue or lesion.
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5. Cytopathology
is the study of cells from various body sites to determine the
cause or nature of disease.
The main applications of Cytopathology include:
Screening for the early detection of asymptomatic cancer
Diagnosis of symptomatic cancer
Follow up of patients treated for cancer.
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Histopathology lecture notes
6. Cyto…
The different types of cytopathologic methods include:
Fine-needle aspiration cytology (FNAC)
Exfoliative cytology
Abrasive Cytology
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Histopathology lecture notes
7. Cyto…
Fine-needle aspiration cytology (FNAC)
In FNAC, cells are obtained by aspirating from the diseased
organ using a very thin needle under negative pressure.
Virtually any organ or tissue can be sampled by Fine-needle
aspiration.
The aspirated cells are then stained and are studied under the
microscope.
Superficial organs (example, breast, lymph node, skin and soft
tissue) can be easily aspirated.
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8. Cyto…
Deep organ lesions, such as the lung, liver, pancreas, kidneys
and adrenal glands are aspirated with guidance by fluoroscopy
or ultrasound.
FNAC is cheap and fast in diagnosing many diseases
e.g., Tuberculosis, lymphoma and others.
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Histopathology lecture notes
10. Cyto…
Exfoliative cytology
Refers to the examination of cells that are shed spontaneously in
to body fluids or secretions.
e.g., sputum, cerebrospinal fluid (CSF), urine, effusions in
body cavities (pleura, pericardium, peritoneum) and vaginal
discharge
can be used for the diagnosis of cancer cells and cancer
markers.
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12. Cyto…
Abrasive cytology
Refers to methods by which cells are dislodged by various
tools from body surfaces such as
skin, mucous membrane, and serous membrane.
The method can be used in preparation of samples for cervical
smear (Pap smear) for early detection of cancer of the uterine
cervix.
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14. Learning objectives
Upon the completion of this chapter, the student should be able to:
o Explain the difference between immunohistochemistry and
immunocytochemistry
o Define polyclonal and monoclonal antibodies
o Discuss methods of antigen retrieval
o Explain methods of antibody staining
o Explain methods of antibody detection
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Histopathology lecture notes
15. 8.1 Introduction
• Immunochemistry is a method used to detect a specific antigen in
the tissue or cells to identify the type of disease.
• In these techniques, an antibody is used to link a cellular antigen
specifically to a stain that can be more readily seen with a
microscope.
• Detection of antigens in tissues is known as
Immunohistochemistry,
• while detection in cultured cells is generally termed
immunocytochemistry.
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16. 8.1 Introduction …
• For both, there is a wide range of
– specimen source, antigen availability, antigen antibody affinity,
antibody type, and detection enhancement methods.
• Thus optimal conditions for immunohistochemical or
immunocytochemical detection
– must be determined for each individual situation, dependent on
the above variables.
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17. Antigen
• Antigen may be protein, carbohydrate, and lipid or a combination.
• On the antigen molecule, there are specific sites for attachment of
antibody molecules.
• The antibody attaching sites on antigens are known as antigenic
determinants or epitopes.
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18. Antibodies
• Antibodies are classes of immunoglobulins.
• There are five classes of antibodies: namely IgG, IgA, IgM, IgE,
and IgD.
• Immunogloblin G (IgG) is the most common and most frequently
used antibody for immunocytochemistry.
• Each immunoglobulin is composed of
– Two light chain and two heavy polypeptide chains joined by a
disulphide bond to form a Y shaped structure.
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19. • The terminal region of each arm varies in their amino acid
sequence and is known as variable domain.
• The variability in amino acid sequence is responsible for a
particular epitope.
• The particular epitope enables the antibody to bind specifically to
the particular antigen for which the antibody is raised.
Antibodies cont’d…
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20. • The amino acid chain on the variable domain forms a cavity.
• The cavity is geometrically and chemically complementary to a
single type of antigen epitope.
• The complementary antigen and antibody are held together
– by a combination of hydrogen bonds, electrostatic forces and
Van-deer Walls forces.
Antibodies cont’d…
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22. Polyclonal antibodies
• The antibodies react major with corresponding antigen and
also react minor with similar antigen.
Monoclonal antibody
• The antibody reacts specifically with its corresponding antigen
and does not react with other antibody even with antibody
having minor viabilities.
Antibodies cont’d…
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Cytopathology is generally used on samples of free cells or tissue fragments, in contrast to histopathology, which studies whole tissues.
Cytopathology is commonly used to investigate diseases involving a wide range of body sites, often to aid in the diagnosis of cancer but also in the diagnosis of some infectious diseases and other inflammatory conditions.[3] For example, a common application of cytopathology is the Pap smear, a screening tool used to detect precancerous cervical lesions that may lead to cervical cancer.
(FNAC), involves use of a needle attached to a syringe to collect cells from lesions or masses in various body organs by microcoring, often with the application of negative pressure (suction) to increase yield. FNAC can be performed under palpation guidance (i.e., the clinician can feel the lesion) on a mass in superficial regions like the neck, thyroid or breast; FNAC may be assisted by ultrasound or CAT scan for sampling of deep-seated lesions within the body that cannot be localized via palpation.
Exfoliative cytology: In this method, cells are collected after they have been either spontaneously shed by the body ("spontaneous exfoliation"), or manually scraped/brushed off of a surface in the body ("mechanical exfoliation"). An example of spontaneous exfoliation is when cells of the pleural cavity or peritoneal cavity are shed into the pleural or peritoneal fluid. This fluid can be collected via various methods for examination. Examples of mechanical exfoliation include Pap smears, where cells are scraped from the cervix with a cervical spatula, or bronchial brushings, where a bronchoscope is inserted into the trachea and used to evaluate a visible lesion by brushing cells from its surface and subjecting them to cytopathologic analysis.
Antigen retrieval refers to any technique in which the masking of an epitope is reversed and epitope-antibody binding is restored.
Polyclonal antibodies are made using several different immune cells. They will have the affinity for the same antigen but different epitopes, while monoclonal antibodies are made using identical immune cells that are all clones of a specific parent cell.
Polyclonal antibodies (pAbs) are mixture of heterogeneous which are usually produced by different B cell clones in the body. They can recognize and bind to many different epitopes of a single antigen. ... Monoclonal antibodies (mAbs) are generated by identical B cells which are clones from a single parent cell.
Why are monoclonal antibodies better than polyclonal antibodies? Because monoclonal antibodies specifically detect a particular epitope on the antigen, they are less likely than polyclonal antibodies to cross-react with other proteins.
