Cellular pathology

Cytopathology (from Greek κύτος, kytos, "a hollow";πάθος, pathos, "fate, harm"; and -λογία, -logia) is a branch of pathology that studies and diagnoses diseases on the cellular level. The discipline was founded by George Nicolas Papanicolaou in 1928. 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. For example, a common application of cytopathology is the Pap smear, a screening tool used to detect precancerous cervical lesions which may lead to cervical cancer.

Cytopathologic tests are sometimes called smear tests because the samples may be smeared across a glass microscope slide for subsequent staining and microscopic examination. However, cytology samples may be prepared in other ways, including cytocentrifugation. Different types of smear tests may also be used for cancer diagnosis. In this sense, it is termed a cytologic smear.

Cytopathology is frequently, less precisely, called cytology, which means "the study of cells."

There are two methods of collecting cells for cytopathologic analysis: exfoliative cytology, and intervention 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. Liquid-based cytology collects the samples in the same way but places them in liquid that is then treated to allow for improved results.

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