Cytology and histology are branches of biology that examine cells and tissues under a microscope. Cytology involves examining individual cells from bodily fluids or tissues to diagnose conditions like cancer, while histology examines the microscopic anatomy of entire tissues and their preparation is more complex. Both are important diagnostic tools, with cytology providing quicker but sometimes less accurate results than histology.

1. CYTOLOGY AND HISTOLOGY
Smital Avinash Garud
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2. WHAT IS CYTOLOGY
cytology (also known as cytopathology) involves examining cells from bodily
tissues or fluid to determine a diagnosis.
Since cytology only examines cells under the microscope, which are so tiny,
pathologist only needs a very small sample of tissue to do a cytology test.
Healthcare providers use cytology in many different areas of medicines, but
cytology tests are most commonly used to screen or diagnose cancer.

3. WHAT KIND OF CYTOLOGY ARE THERE
• There are two main branches of cytology: Exfoliative cytology and Intervention cytology
• Some common types of cytology test includes:
1. Gynecologic cytology
2. Breast cytology
3. Thyroid cytology
4. Respiratory cytology
5. Eye cytology
6. Ear cytology
7. Lymph node cytology

4. WHAT IS EXFOLIATIVE CYTOLOGY ?
• It is the microscopic examination of shed cells from body surfaces or cells harvested by rubbing
or brushing a lesioned tissue surface.
• It is introduced by Papanicolaou in 1941.
• It’s a simple, pain-free, noninvasive, and rapid technique.
• E. g. gastrointestinal sample, skin or mucous sample, urinary sample, etc.

5. WHAT IS INTERVENTIONAL CYTOLOGY ?
• This is the branch of cytology in which samples are obtained by clinical procedure or surgical
intervention.
• It is also known as aspiration cytology.
• It includes fine needle aspiration cytology (FNAC), biopsy, imprint cytology and crush smear
cytology.

6. WHEN IS CYTOLOGY IS USED ?
• Healthcare providers and pathologists most commonly use cytology to diagnose or screen cancer.
• Some other uses of cytology test includes:
1. To diagnose infectious diseases.
2. To diagnose inflammatory conditions.
3. To examine thyroid lesions.
4. To diagnose disease involving certain body cavities, such as space between two thin
membranes that line and surround your lungs (pleural cavity).

7. HOW DOES A CYTOLOGY TEST WORK ?
• Each cytology test is slightly different depending on what kind of cells are being tested and if the
sample is tissue or fluid.
• There are four steps to cytology test including:
1. Collecting the sample cell.
2. Processing the sample cell.
3. Examining the sample cell.
4. Sharing the result.

8. BENEFITS
cytology tests have many benefits due to the small amount of tissue and fluid sample needed for
the test. They are also used to determine a diagnosis, through a cytology test.
1. It is less invasive
2. Causes less discomfort and pain
3. Costs less
4. To less likely to cause complications

9. DISADVANTAGES
• Complications from cytology tests are very rare and if they happen, they are often mild.
Sometimes cytology tests can give a false negative or false positive result. In some cases, tissue
biopsies can be more accurate than cytology tests.

10. WHAT IS HISTOLOGY
• Histology is also known as microscopic anatomy or microanatomy. It is the branch of biology
which studies the microscopic anatomy of biological tissues.
• It is an important part of anatomical pathology and surgical pathology, as accurate diagnosis of
cancer and other diseases often requires histopathological examination of the tissue sample.

11. Steps of histological slide preparation:
1. Tissue fixation
slide preparation begins with the fixation of a tissue specimen. Specimens can be fixed in 10%
neutral buffered formalin. For best results, biological tissue samples should be transferred into
fixative immediately after collection.
2. Specimen transfer to cassettes
After fixation, specimens are trimmed using a scalpel to enable them to fit into an appropriately
labeled tissue cassette.
3. Tissue processing
Processing tissues into thin microscopic sections is usually done using paraffin, as follows:
a. Dehydration involves immersing a specimen in increasing concentrations of alcohol to
remove the water and formalin from the tissue.
b. Clearing, in which an organic solvent such as xylene is used to remove the alcohol and
allow infiltration with paraffin wax.
c. Embedding, where specimens are infiltered with the embedding agent- usually paraffin wax.
The tissue becomes surrounded by a large block of molten paraffin wax, creating what is
now referred to as the “block”.

12. 4. Sectioning
a. Wax is removed from the surface of the block to expose the tissue.
b. Blocks are chilled on a refrigerated plate or ice tray for 10 minutes before sectioning.
c. A microtome is used to slice extremely thin tissue sections off the block in the form of a
ribbon.
5. Staining
a. histochemical stain typically hematoxylin and eosin is therefore used to provide contrast to
tissue sections, making tissue structures more visible and easier to evaluate.
b. A coverslip is mounted over the tissue specimen on the slide, using optical grade glue, to
protect the specimen.

13. Difference between cytology and histology:-
Cytology Histology
The branch of biology and medicine
concerned with the structure and function
of plant and animal cell
The study of microscopical anatomy of
tissues.
Narrow study area Wide study area
The slide preparation is simple The slide preparation is complex
Less expensive More expensive
Studies of cellular areas of cell Studies the architecture of tissues