Two broad categories of samples are received in the cytology laboratory:

1. Exfoliative cytology: It is the study of cells that have been shed or removed from the epithelial or mesothelial linings. Normal cells are cohesive in nature, but malignancy and infection increase exfoliation. Malignant cells show reduced intercellular adhesion due to defective desmosomes. These cells can be recovered either from natural secretions. Such as urine, sputum, vaginal, and prostatic fluids, or by artificial means, such as paracentesis or lavage of fluids like pleural, pericardial, cerebrospinal, synovial, ascetic, CSF, cyst fluid, bronchial washings etc. 

2. Fine needle aspiration cytology includes aspiration done by the pathologist or the clinician as well as guided aspiration done by the radiologists and aspirations. It is a diagnostic procedure used to investigate pathological lesions in organs that do not shed cells spontaneously. In this technique, a thin, hollow needle is inserted into the lesion (usually a lump or a swelling) to obtain cells and tissue fragments, which, after being stained, are examined under a microscope.