cytologie

Cytologie is a branch of pathology focused on the study of cells in health and disease. It aims to assess cell morphology, identify cellular abnormalities, detect infectious agents, and support clinical management through minimally invasive sampling. Cytology covers exfoliative cytology, which uses shed cells from mucous membranes and serous surfaces, and aspiration cytology, where cells are collected from masses or organs using needles. It is distinct from histology, which analyzes tissue architecture.

Historically, cytology developed with advances in microscopy, and the cervical cancer screening Pap smear by Papanicolaou in the 1920s marked a major milestone. Today, cytology is integral to screening programs and diagnostic workups, and cytopathology is the medical specialty focused on interpreting cytologic preparations and guiding treatment.

Techniques include sample collection methods (exfoliative samples and fine-needle aspirations), preparation as smears or cell blocks, and staining with Papanicolaou, Giemsa, or Diff-Quik. Slides are examined under light microscopy, and ancillary methods such as immunocytochemistry, flow cytometry on selected specimens, and molecular assays can enhance diagnostic yield.

Applications encompass cancer screening (notably cervical cytology), diagnosis of neoplastic and non-neoplastic conditions, detection of infections, and analysis of body fluids such as cerebrospinal, pleural, and peritoneal fluids, as well as urine sediments and aspiration specimens from various sites. The Pap test has contributed to reduced cervical cancer incidence in many regions.

Limitations include the lack of tissue architecture, which may require histologic correlation; sampling variability can lead to false negatives; and interpretation depends on specimen quality and expertise. The field emphasizes multidisciplinary collaboration and increasingly employs automation, liquid-based cytology, and molecular cytopathology to improve accuracy.