Cytopathology

Cytopathology is a branch of pathology that focuses on the cytologic study of cells collected from tissues and body fluids to diagnose disease, especially cancer. It emphasizes cellular morphology rather than tissue architecture, enabling rapid, minimally invasive assessment. The field includes exfoliative cytology, such as Pap tests, urine cytology, and effusion cytology, as well as aspiration cytology obtained by fine-needle aspiration (FNA) of masses; bronchial washings, sputum, and lavage samples are also examined.

Specimens are prepared by smears or liquid-based cytology, and may be evaluated with staining methods such as Papanicolaou or Romanowsky-type stains. In some cases, cell blocks are prepared to permit histology-like sections and ancillary studies.

Ancillary techniques include cytochemistry and immunocytochemistry performed on cytology specimens, as well as molecular testing from cell blocks for mutations, rearrangements, and other biomarkers. Flow cytometry can be applied to certain cytology samples, particularly lymphoid lesions.

Applications and interpretation: Pap smear screening, diagnosis of malignancy and infections, grading of tumor cells, and identification of metastatic disease. Cytology can provide rapid preliminary diagnoses, guide management, and in many cases obviate the need for invasive biopsy. However, limitations include lack of preserved architectural context, sampling error, and false positives/negatives; correlation with clinical findings and, when needed, histopathology is essential.

History and professionals: The field traces its modern form to the Pap smear developed by George Papanicolaou and colleagues in the 1940s. Cytopathology is practiced by pathologists and cytotechnologists who prepare, screen, and interpret specimens.