Specimen Collection - Catching Culprits
- Key Goal: Obtain adequate, representative cells for diagnosis.
- Methods Overview:
| Specimen | Collection | Adv. | Disadv. | Yields |
|---|---|---|---|---|
| Sputum | Deep cough, 3-5 early AM samples | Non-invasive, cost-effective | Low sensitivity (peripheral), oral flora | Inflammatory cells, organisms, tumor (central) |
| BAL | Bronchoscope, saline wash (distal airways) | Samples alveoli, good for diffuse | Invasive | Macrophages, lymphocytes, organisms, tumor |
| Bronchial Brush/Wash | Bronchoscope, direct brushing/wash of lesion | Samples visible lesions, ↑cells | Invasive, bleeding risk | Tumor (central), bronchial, inflammatory |
| FNA (TTNA/EBUS) | Needle aspirate (CT/US/EBUS guided) | Peripheral/mediastinal, high yield | Invasive, pneumothorax risk | Tumor, granulomas, lymphocytes |
⭐ For suspected pulmonary TB, 3-5 consecutive early morning sputum samples are recommended for AFB smear/culture to maximize diagnostic yield.
Benign & Reactive - The Usual Suspects
- Normal Cellular Components:
- Ciliated columnar (benign indicator), goblet (mucin), basal (reserve) cells.
- Alveolar macrophages (dust cells, phagocytic).
- Reactive Atypia & Inflammation:
- Inflammatory cells: Neutrophils, lymphocytes, eosinophils.
- Epithelial changes: Nuclear enlargement, prominent nucleoli. Ciliocytophthoria.
- Creola bodies: 3D clusters of reactive bronchial cells; benign mimic of malignancy.
- Common Infections - Key Features:
- Aspergillus: Septate hyphae, acute (45°) angle branching.
- Candida: Pseudohyphae, budding yeasts.
- CMV: Large cells, "Owl's eye" basophilic intranuclear inclusions.
- HSV: Multinucleation, nuclear molding, ground-glass chromatin (Cowdry A).
⭐ Creola bodies are benign reactive bronchial cell clusters that can significantly mimic adenocarcinoma due to their 3D structure and atypia.
Squamous Lesions - From Mild to Malignant
- Squamous Metaplasia: Benign; flat, polygonal cells, small regular nuclei, normal N/C ratio.
- Dysplasia (Squamous Intraepithelial Lesion - SIL):
- Low-grade (LSIL): Mildly ↑N/C ratio, slight hyperchromasia, smooth nuclear outlines.
- High-grade (HSIL): Moderately to markedly ↑N/C ratio, hyperchromasia, irregular nuclear outlines, coarse chromatin.
- Squamous Cell Carcinoma (SCC): Malignant cells, often individual or in poorly cohesive sheets.
- Key Features: Dense, often orangeophilic/eosinophilic cytoplasm (keratinization), bizarre cell shapes (tadpole, spindle cells 📌 "Tadpoles swim in keratin seas"), hyperchromatic, irregular nuclei. Necrotic/inflammatory background common.
- Keratinizing SCC: Obvious keratin (dense orangeophilia, pearls).
- Non-keratinizing SCC: Less keratin, prominent nucleoli.
⭐ SCC is the most common lung cancer type linked to smoking; centrally located, often cavitates. P63 and CK5/6 are positive IHC markers for SCC (though typically for histology).
Glandular & Large Cell - Adeno & Beyond
-
Adenocarcinoma (ADC):
- Cytologic features: 3D clusters, acini, papillae; vacuolated cytoplasm; prominent nucleoli. Signet rings (rare in cytology).
- Adenocarcinoma in situ (AIS)/Lepidic: May show bland, cohesive clusters or flat sheets.
-
Large Cell Carcinoma (LCC):
- Diagnosis of exclusion.
- Features: Large undifferentiated cells, prominent nucleoli, moderate cytoplasm; no glandular/squamous differentiation.
⭐ TTF-1 and Napsin A are crucial immunohistochemical (IHC) markers for identifying pulmonary adenocarcinoma.
Neuroendocrine & IHC - Tiny Terrors, Tell-Tale Stains
- SCLC (Small Cell Lung Carcinoma):
- Cells 2-3x lymphocyte size, scant cytoplasm, nuclear molding.
- "Salt & pepper" chromatin, high N:C ratio, Azzopardi effect (DNA on vessel walls).
- Carcinoid Tumors:
- Uniform, round/plasmacytoid cells; "salt & pepper" chromatin.
- Less atypia/mitoses than SCLC.
- Key IHC Markers:
- Adeno: TTF-1, Napsin A.
- Squamous: p40, p63.
- Neuroendocrine (SCLC, Carcinoid): Synaptophysin, Chromogranin, CD56.
- Common Lung Metastases (Key IHC):
- Breast: GATA3; Colon: CDX2, CK20; Melanoma: S100, SOX10.
⭐ > SCLC is notorious for paraneoplastic syndromes (e.g., SIADH, Lambert-Eaton).
High‑Yield Points - ⚡ Biggest Takeaways
- Sputum cytology is best for central lung tumors; BAL for peripheral lesions and diffuse diseases.
- Charcot-Leyden crystals and Curschmann spirals are key findings in bronchial asthma.
- Ferruginous bodies (asbestos bodies) are diagnostic markers for asbestosis.
- Small cell carcinoma shows nuclear molding, salt-and-pepper chromatin, and scant cytoplasm.
- Adenocarcinoma often presents with glandular clusters, prominent nucleoli, and intracytoplasmic mucin.
- Squamous cell carcinoma is characterized by keratinization, intercellular bridges, and dense cytoplasm.
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