Paper I
Question
Exfoliative cytology
Answer
Exfoliative cytology is the study of cells that have spontaneously desquamated (shed) from epithelial surfaces, or been dislodged by mild scraping/brushing, examined microscopically for diagnostic purposes.
Principle
- Cells are collected from a body surface or fluid, spread on a glass slide, fixed (usually with 95% ethyl alcohol), and stained (commonly Papanicolaou stain) for cytological examination
Common applications
- Papanicolaou (Pap) smear: Cervical exfoliative cytology — screening for cervical intraepithelial neoplasia and cervical carcinoma
- Sputum cytology — for lung malignancy
- Urine cytology — for bladder malignancy
- Body fluid cytology (pleural, peritoneal, CSF) — for detecting malignant cells in effusions
Advantages
- Minimally invasive, simple, cost-effective, suitable for population screening
- Can detect preinvasive/early lesions before they become clinically or radiologically apparent
Limitations
- Cannot assess tissue architecture/invasion (unlike histopathology)
- Sampling error possible; false negatives can occur
- Diagnosis of malignancy on cytology alone is usually followed by histopathological confirmation (biopsy)