A certain kind of physician, called a pathologist, will look at the cells in the tissue sample under a microscope and look for characteristics or abnormalities in the cells.
Since cytology only examines cells, which are so tiny, pathologists only need a very small sample of tissue to do a cytology test..
Guidelines from the College of American Pathologists (CAP), therefore, recommend sending as much fluid volume as attainable to the cytology laboratory for triage and subsequent workup when there is a high index of suspicion for malignancy.
Sensitivity is a characteristic of fluid cytology (the test) and influenced by test characteristics and selected criteria for positivity.
Diagnostic yield, however is highly dependent on the pretest probability of MPE in the studied population.
Although there is some merit to repeating pleural fluid analysis, the diagnostic yield with subsequent pleural fluid aspirations decreases substantially.
The true yield of a second pleural fluid cytology is not well known.
In most cases, a definitive malignant diagnosis can be rendered on the basis of the cytomorphologic evaluation alone, although in a subset of cases, IHC analysis is performed to confirm the diagnosis and establish the primary site of malignancy.
