Cytopathology 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 study a wide range of body sites, often to aid in the diagnosis of cancer, but also in the diagnosis of certain infectious diseases and other inflammatory conditions. For example, a common application of cytopathology is Pap smear, a screening tool used to detect precancerous cervical lesions that can lead to cervical cancer. Cytopathological tests are sometimes called smear tests because they can be spread on a glass microscope slide for later staining and microscopic examination. However, cytology samples can be prepared by other means, including cytocentrifugation. Different types of smear tests can also be used to diagnose cancer. In this sense, it is called cytological smear.

Cytopathology is best used as one of three tools, the second and third being physical examination and medical imaging. Cytology can be used to diagnose a condition and spare a patient a larger sample. An example is the FNAC thyroid; Many benign conditions can be diagnosed with a superficial biopsy and the patient can resume normal activities immediately. If a malignancy is diagnosed, the patient may be able to start radiation therapy / chemotherapy, or may need surgery to remove and / or stage the cancer. Some tumors can be difficult to biopsy, such as sarcomas. Other rare tumors can be dangerous for biopsy, such as pheochromocytoma. In general, fine needle aspiration can be done anywhere, including the liver, lungs, kidneys and surface masses