Pathology Cheat Sheet
Cells Need Context
Diagnostic cytology for NEET-PG: exfoliative vs FNAC, Papanicolaou stain, liquid-based cytology, fixation, and the role and limits of cell-based diagnosis.
MedNext Academy | 3 min read
Cells Need Context
Diagnostic cytology for NEET-PG: exfoliative vs FNAC, Papanicolaou stain, liquid-based cytology, fixation, and the role and limits of cell-based diagnosis.
The diagnostic role of cytology and the basis, techniques and stains of exfoliative and aspiration cytology.
High-yield lines
- Cytology examines individual cells and small cell groups rather than intact tissue architecture.
- Exfoliative cytology studies cells that are naturally shed or scraped from epithelial surfaces, as in the cervical Pap smear.
- Fine-needle aspiration cytology samples cells from palpable or image-guided masses using a thin needle.
- The Papanicolaou stain is the standard stain for exfoliative cytology and gives excellent nuclear detail.
- Cytology is rapid, minimally invasive, and inexpensive, making it valuable for screening and initial assessment.
- The main limitation of cytology is loss of architecture, so it cannot always distinguish in-situ from invasive disease.
- May-Grunwald-Giemsa staining is often used for aspirates and highlights cytoplasmic and background features.
- Adequate fixation, ideally immediate, prevents air-drying artefact that distorts nuclear detail on Pap staining.
- Cervical cytology screening detects precancerous squamous lesions at the transformation zone.
- Liquid-based cytology improves cell preservation and reduces obscuring blood and inflammation.
- A definitive malignant diagnosis on cytology often still requires biopsy confirmation before major surgery.
- Cytology can be applied to body fluids such as pleural, peritoneal, and cerebrospinal fluid to detect malignant cells.
Mapped competency codes
- PA8.1
- PA8.2
Continue into the full chapter
This summary maps to PA8-basic-diagnostic-cytology.
Frequently Asked Questions
What is the difference between exfoliative and aspiration cytology?
Exfoliative cytology studies naturally shed or scraped surface cells such as a Pap smear, while fine-needle aspiration cytology samples cells directly from a mass with a thin needle.
Which stain is standard for exfoliative cytology?
The Papanicolaou stain, which provides excellent nuclear detail and transparent cytoplasm for assessing shed epithelial cells.
What is the main limitation of cytology?
It examines individual cells without tissue architecture, so it cannot always separate in-situ from invasive lesions and may need biopsy confirmation.
Why is prompt fixation important in cytology?
It prevents air-drying artefact that distorts nuclear detail and reduces the accuracy of Papanicolaou-stained smears.
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