Basic Principles of Cytopathology

Basic Principles of Cytopathology

Basic Principles of Cytopathology

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Introduction & Specimen Types - Tiny Tissue Tales

Cytopathology: Diagnostic study of cells obtained from various body sites. Evaluates cell morphology for screening, diagnosis, and prognosis.

  • Advantages: Minimally invasive, rapid turnaround, cost-effective.
  • Disadvantages: Loss of tissue architecture, potential sampling errors, operator dependent. Specimen Types:
  • Exfoliative: Cells shed naturally or collected by mechanical means.
    • Spontaneous: Sputum, urine, CSF, serous effusions (pleural, peritoneal, pericardial).
    • Mechanical: Pap smear, bronchial brushings/washings, GIT brushings.
  • Fine Needle Aspiration Cytology (FNAC): Cells aspirated using a 22-27 gauge needle.
    • Palpable lesions: Thyroid, lymph node, breast, salivary gland, soft tissue.
    • Non-palpable (image-guided): Lung, liver, pancreas, kidney.
  • Imprint/Touch Cytology: Cells transferred from fresh biopsy surface.

⭐ FNAC is often the first line investigation for palpable lumps due to its speed and minimal invasiveness.

Cellular Morphology & Malignancy - Spotting Bad Guys

Distinguishing malignant cells from benign involves scrutinizing key cellular features. Malignancy often presents with a constellation of changes, not just one.

  • Nuclear Criteria (Most Reliable): 📌 PINCH-M
    • Pleomorphism: Variation in nuclear size & shape.
    • Increased N/C Ratio: Nucleus occupies much larger cell proportion (e.g., > 0.5 or 1:2, can approach 1:1).

      ⭐ A significantly ↑ N/C ratio is a primary indicator of malignancy.

    • Nucleoli: Prominent, irregular, or multiple.
    • Chromatin: Coarsely clumped, irregular distribution; parachromatin clearing.
    • Hyperchromasia: Darkly stained nuclei due to ↑ DNA.
    • Membrane: Irregular nuclear outline, indentations, grooves.
  • Cytoplasmic Features:
    • Variable amount (often scant in high-grade tumors).
    • Altered staining (e.g., basophilic due to ↑ ribosomes).
    • Vacuolization (e.g., signet ring cells).
  • Cellular Arrangement & Background:
    • Loss of cohesion & polarity.
    • Cellular crowding, overlapping, disorganization.
    • Mitotic figures: ↑ number, atypical forms (e.g., tripolar, multipolar).
    • Tumor diathesis: Necrotic debris & old blood in background (common in exfoliative cytology).

Mixed content: histology, IHC, and gene diagram

Specimen Collection & Processing - Prepping the Slides

  • Collection Methods:
    • FNA: Fine Needle Aspiration for palpable/deep lesions.
    • Exfoliative: Naturally shed cells (urine, sputum).
    • Abrasive: Scraping/brushing surfaces (Pap smear).
  • Slide Preparation:
    • Smearing: Create thin, even cell layer.
      • Direct smears: For cellular samples.
      • Cytocentrifugation (Cytospin): Concentrates cells in hypocellular fluids (CSF).
      • Liquid-Based Cytology (LBC): Reduces debris, uniform distribution.
    • Fixation: Preserves morphology, prevents autolysis. 📌 A-P, A-R (Alcohol-Pap, Air-Romanowsky).
      • 95% Ethanol: Standard for Pap (immediate wet fix).
      • Spray fixatives: Carbowax-based (for Pap smears).
      • Air drying: For Romanowsky stains (MGG, Giemsa).
    • Staining: Highlights structures for diagnosis.
      • Papanicolaou (Pap): Excellent nuclear detail; polychromatic cytoplasm.
      • Romanowsky (MGG, Giemsa): Good cytoplasmic, matrix, granule detail.

⭐ Immediate fixation in 95% ethanol is crucial for optimal Pap staining, preventing air-drying artifacts.

Cytopathology slide preparation: Smear technique

Screening & Diagnostic Applications - Cytology's Big Hits

  • Screening Triumphs:
    • Cervical Cancer: Pap smear detects pre-malignant (dysplasia) & malignant changes.
    • Urine Cytology: For bladder cancer screening in high-risk groups & surveillance.
  • Diagnostic Powerhouses:
    • FNAC: Go-to for palpable (thyroid, breast, lymph nodes) & deep lesions (image-guided).
    • Exfoliative Cytology: Cells from surfaces (pleural, peritoneal, CSF fluids; sputum).
    • Brushings & Lavages: Direct sampling from respiratory (bronchial) & GI tracts.

⭐ Pap smear screening has reduced cervical cancer incidence & mortality by over 70% in many regions.

Cytology applications: Pap smear, FNAC, bronchial brushing

High‑Yield Points - ⚡ Biggest Takeaways

  • Cytopathology diagnoses diseases, especially cancer, by examining individual cells or cell clusters.
  • Sampling methods: exfoliation, abrasion (e.g., Pap smear), and Fine-Needle Aspiration (FNA).
  • FNA is key for palpable/deep lesions; Pap smear is vital for cervical cancer screening.
  • Diagnosis relies on nuclear criteria (size, N/C ratio, chromatin, nucleoli) and cytoplasmic features.
  • Advantages include being minimally invasive, offering rapid results, and cost-effectiveness.
  • Limitations: potential for sampling error and absence of tissue architecture compared to histopathology.

Practice Questions: Basic Principles of Cytopathology

Test your understanding with these related questions

Arrange the following in sequential order with regards to the steps of collection of samples for pap smear testing: Use posterior vaginal wall retractor Take the sample Make smear on a slide Fix the smear

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Flashcards: Basic Principles of Cytopathology

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According to the Bethesda system (Thyroid cytopathology), what is the preferred line of Mx for Criteria III?_____

TAP TO REVEAL ANSWER

According to the Bethesda system (Thyroid cytopathology), what is the preferred line of Mx for Criteria III?_____

Repeat FNA or lobectomy

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