Fine Needle Aspiration Cytology

Fine Needle Aspiration Cytology

Fine Needle Aspiration Cytology

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FNAC Fundamentals - Point & Shoot

  • Definition: Diagnostic procedure using a fine needle to aspirate cells from a lesion for microscopic examination.
  • Principle: Cellular material obtained by suction through a needle, smeared on a slide, stained, and evaluated.
  • Advantages: 📌 S.A.F.E.R - Simple, Accurate, Fast, Economical, Reliable. Minimally invasive.
  • Disadvantages: Sampling error (may miss lesion), no tissue architecture, operator dependent.
  • Indications: Palpable lesions (thyroid, breast, lymph nodes), image-guided for deep lesions (lung, liver).
  • Contraindications: Severe bleeding diathesis, uncooperative patient, overlying infection (relative).

⭐ FNAC is a rapid, minimally invasive, and cost-effective diagnostic tool, often the first line of investigation for palpable masses.

FNAC Workflow - Poke, Smear, Stain

1. Poke (Aspiration):

  • Needle: Typically 22-25 gauge; length varies.
  • Syringe: 10-20 ml, often pistol grip for single-hand operation.
  • Techniques:
    • Suction: using syringe for negative pressure.
    • Non-aspiration (Zajdela/capillary technique): uses capillary action of fine needle.

2. Smear (Slide Preparation):

  • Expel material onto slide.
  • Methods:
    • Direct smear.
    • Pull-apart/slide-over-slide (common).
    • Crush: for cellular/fragmented material. FNAC Smearing Techniques

3. Stain (Fixation & Staining):

  • Fixation & Stains:
    • Air-drying: For Romanowsky (e.g., MGG, Giemsa); highlights cytoplasm, matrix.
    • Wet fixation: 95% ethanol for Papanicolaou (Pap - nuclear detail, keratin) & H&E (general morphology).

⭐ The choice of fixation and staining (Air-dried/Romanowsky vs. Alcohol-fixed/Pap) depends on the suspected diagnosis and institutional preference, each highlighting different cellular features.

FNAC Procedure Flowchart:

Cytological Interpretation - Decoding the Cells

  • Specimen Adequacy:
    • Sufficient cellularity
    • Presence of diagnostic cells
    • Absence of obscuring elements (blood, clot)
  • General Cytomorphological Features:
    • Background: Clean, bloody, inflammatory, necrotic
    • Arrangement: Clusters, sheets, acini, papillary, single cells
    • Cell: Size, shape
    • Nucleus: N:C ratio, chromatin (fine/coarse), membrane (smooth/irregular), nucleoli (inconspicuous/prominent)
    • Cytoplasm: Amount, color, granules, vacuoles, inclusions
  • Criteria of Malignancy: 📌 Mnemonic: Ugly Nuclei
    • Anisokaryosis/Pleomorphism
    • Hyperchromasia
    • Irregular nuclear contours
    • Prominent/multiple nucleoli
    • ↑ N:C ratio
    • Abnormal mitoses
  • Reporting Systems:
    • Bethesda (Thyroid)
    • Milan (Salivary Gland)
    • IAC Yokohama (Breast)
    • Paris (Urine)

⭐ Accurate interpretation requires assessing both individual cell morphology and the overall architectural pattern of cell groups, alongside clinical context.

Organ-Specific FNAC - Target Practice

  • Thyroid:
    • Hashimoto's: Lymphocytes, Hürthle cells.
    • Papillary Ca: Nuclear grooves, intranuclear inclusions, psammoma bodies.
    • General: Colloid, follicular cells.
  • Lymph Node:
    • Reactive Hyperplasia: Polymorphic lymphoid population.
    • TB Lymphadenitis: Epithelioid granulomas, Langhans giant cells, caseous necrosis.
    • Metastasis: Foreign cells.
  • Breast:
    • Fibroadenoma: Staghorn clusters of ductal cells, bipolar naked nuclei.
    • Ductal Carcinoma: Cellular, discohesive malignant cells, pleomorphism.
  • Salivary Gland:
    • Pleomorphic Adenoma: Chondromyxoid stroma, epithelial/myoepithelial cells.

Psammoma bodies in Papillary Thyroid Carcinoma FNAC

⭐ In thyroid FNAC, nuclear features like grooves, inclusions, and powdery chromatin are key to diagnosing Papillary Thyroid Carcinoma, even with scant cellularity.

High‑Yield Points - ⚡ Biggest Takeaways

  • FNAC is a minimally invasive, cost-effective, and rapid diagnostic tool.
  • Uses fine needles (typically 22-27 gauge) for cellular material aspiration.
  • Key for evaluating palpable lesions: thyroid nodules, breast lumps, lymph nodes.
  • Image guidance (USG/CT) is vital for non-palpable or deep-seated lesions.
  • ROSE ensures sample adequacy, reducing need for repeat procedures.
  • Effectively differentiates benign vs. malignant conditions, guiding management.
  • Complications like hematoma are rare and generally minor.

Practice Questions: Fine Needle Aspiration Cytology

Test your understanding with these related questions

A 26-year-old male presents to the outpatient department with a discrete thyroid swelling. On neck ultrasound, an isolated cystic swelling of the gland is seen. What is the risk of malignancy associated with this finding?

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Flashcards: Fine Needle Aspiration Cytology

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A Thy4 FNAC result defines the thyroid lesion as _____

TAP TO REVEAL ANSWER

A Thy4 FNAC result defines the thyroid lesion as _____

suspicious of malignancy

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