Cytology is the exam of a single cell. These cells are often found in fluid samples. Cytology is used to do the following:

• Diagnose or screen for cancer or diseases
• Screen for fetal abnormalities
• Screen for Pap tests
• Diagnose infectious organisms
• Work with other screening and diagnostic areas

The cells to be examined may be taken by these methods:

• Scraping or brushing the tissue surface, such as during a Pap test
• Collecting body fluids, such as for urine or respiratory mucus (phlegm)
• Removing cells by drawing them through a fine needle (fine-needle aspiration), such as abdominal fluid in ascites, pleural fluid from the lungs, cells from a thyroid nodule, or cerebrospinal fluid from the spinal canal
• Doing other types of tissue biopsy

Cytology is different from histology. Cytology generally means looking at a single cell on its own. Histology is looking at an entire block of tissue that is made up of many cells.