Basics of Cytopathology

‘Cyto’ refers to the study of cells, and pathology refers to the study of disease. So, cytopathology is the branch of science that studies diseases at the cellular level. Laboratory-based pathologists and other laboratory personnel perform tests related to cytopathology.

Cytopathology is mainly used in pathology to detect and diagnose the presence of cancer-forming cells. Other than that, it is helpful in diagnosing any other disease at the cellular level.

Samples associated with cytology allow the study of the shape, structure, size, and morphology of the cells. Most of the samples are body fluids or secretions.

Key Highlights About Cytopathology:

• Study of individual cells for disease diagnosis

• Minimally invasive sample collection

• Common specimens: Pap smear, fine-needle aspiration (FNA), body fluids

• Focus on cellular morphology (nucleus, cytoplasm, chromatin)

• Rapid turnaround time

• Cost-effective diagnostic method

• Excellent for cancer screening and early detection

• Useful for evaluating infectious, inflammatory, and neoplastic conditions

• Limited assessment of tissue architecture

• Often used as an initial diagnostic tool before biopsy

Common Cytopathology Tests

Some common types of cytopathology tests involving different sample types include:

• Body fluid Cytology

• Cervical Cytology

• Urine Cytology

• Sputum Cytology

• Fine Needle Aspiration Cytology

Objective of Cytopathology:

The main objective of cytopathology is the study of cells and features having roles in the pathological conditions, and the tests performed are used to find out the diseases marked by the changes in the number and features of those cells present in the sample. It is also applicable for the quick, reliable results that don’t need a lengthy time for processing and reporting.

The main aims of cytopathology in human health:

• To diagnose the inflammatory conditions

• To diagnose the infections in different organs and body parts

• To diagnose the tumors

Types of Cytopathology

1. Exfoliative cytology:

The examination of cells in samples shed by the body, such as sputum, urine, body fluid, CSF, and various discharges from different parts of the body. Body fluids are present in various body cavities, such as pleural fluid, peritoneal fluid, synovial fluid, pericardial fluid, and cerebrospinal fluid. These samples are tested for the cellular presence for the diagnosis of various diseases, as already mentioned.

2. Abrasive cytology

It is an examination of cells which required procedure to obtain the cells, such as swabbing, brushing, washing, scraping, etc. Some of the major samples obtained by these procedures are pap smear, vaginal swab, throat swab, broncho-alveolar lavage, skin or mucus membrane scrapings, etc.

3. Intervention/ aspiration cytology

In cytology, the cells are studied in the sample obtained by aspirating the fluid from the lumps and masses that are not normal in the healthy body. These masses can mostly be felt from the outside, such as enlarged lymph nodes, thyroid nodules, breast lumps, and other masses. It is also called Fine Needle Aspiration Cytology (FNAC), as a needle is used to obtain samples and cells from the site.

General Flow-Chart for Cytology Test in the Cytopathology Lab

The cytology tests are different according to the sample to be taken and the sites from which the sample is taken.

1. Collection of the sample:

The sample is obtained as needed by your health care providers for the examination of the cells in that sample. The procedure to obtain a sample varies according to the type of cytology and sample, which was already mentioned above.

2. Transport of the sample to the lab:

The sample obtained is sent to the lab, and the samples, if needed, have to be preserved in preservatives before being sent to the lab or after being obtained in the lab. These samples are either air-dried on glass slides as a smear or sent in sterile containers or vials as per the needs of the tests. Alcohols and formalin are the most commonly used preservatives if needed to preserve the sample in cytopathology.

3. Preparation of the sample for examination:

The samples are prepared according to the type, such as cells from body fluids and lavage and washing, which might need separation for microscopical evaluation, but not in flow cytometry. In case of brushing and swabbing, direct cytological smears can be made and fixed. These smears are further stained (following staining procedures such as Pap and Giemsa), dried, and mounted.

Major stains used in the cytopathology laboratory:

• Papanicolaou Stain

• Romanowsky Stains

• Special Stains (PAS, GMS, AFB, Congo Red)

4. Examination of the sample

A cytologist or laboratory technologist examines the smear in the slides under the microscope for changes and abnormalities. The smears are verified by a pathologist if needed for reporting. The reporting is done according to the shape, structure, quantity, and color of dye taken by cells in the processed smear. Further nuclear and cytoplasmic features, along with their ratio, are also key aspects when reporting for the tests.

5. Creation of the report:

The pathologist provides a final report that shows their findings and diagnosis of the cytology. The correlation with other reports from imaging and clinical findings is also necessary.

Differences Between Cytopathology and Histopathology

Here are the key differences between cytopathology and histopathology:

Feature Cytopathology Histopathology

Specimen Type Cells and body fluids Tissue biopsies and surgical specimens

Collection Method Fine-needle aspiration (FNA), Biopsy and excision Pap smear

Diagnostic Focus Cellular morphology Tissue architecture and morphology

Invasiveness Minimally invasive More invasive

Turnaround Time Faster Slower

References

1. Cibas, E. S., & Ducatman, B. S. (2020). Cytology: Diagnostic principles and clinical correlates (6th ed.). Elsevier.

2. Koss, L. G., & Melamed, M. R. (2005). Koss’ diagnostic cytology and its histopathologic bases (5th ed.). Lippincott Williams & Wilkins.

3. Gray, W., & Kocjan, G. (2020). Diagnostic cytopathology (4th ed.). Elsevier.