Pathology Practical and Stains Revision Guide OmpathStudy

Pathology Practical Revision Guide — Stains Reference General Histopathology Stain Haematoxylin and Eosin (H&E) The routine stain used for all tissue sections. Haematoxylin stains nuclei blue/purple (basophilic structures) Eosin stains cytoplasm and extracellular matrix pink (acidophilic structures) Special Stains and What They Detect 1. Ziehl-Neelsen (ZN) stain — acid-fast bacilli ( Mycobacterium tuberculosis , M. leprae ) 2. Periodic Acid-Schiff (PAS) — glycogen, fungal cell walls, basement membranes, mucin 3. Masson's Trichrome — collagen and fibrosis (collagen stains blue/green, muscle stains red) 4. Congo Red — amyloid deposits (shows apple-green birefringence under polarized light) 5. Reticulin stain — reticulin fibers; used to assess liver architecture and bone marrow fibrosis 6. Prussian Blue (Perls' stain) — iron deposits/haemosiderin; used in haemochromatosis and iron overload 7. Mucicarmine — mucin; confirms mucin-producing adenocarcinomas and stains Cryptococcus capsule 8. Gram stain — bacterial classification (gram-positive vs gram-negative) 9. Grocott's Methenamine Silver (GMS) — fungal organisms ( Pneumocystis , Aspergillus , Candida ) 10. Oil Red O — neutral lipids/fat; used on frozen sections since fat dissolves during routine paraffin processing 11. Von Kossa stain — calcium deposits 12. Papanicolaou (Pap) stain — routine cytology stain (cervical smears, sputum, body fluids) 13. Giemsa / Diff-Quik — rapid on-site cytology staining; also used for malaria parasites and blood films Cytology-Specific Fixatives 95% ethanol — wet fixation for Pap-stained cytology preparations Air-drying — used when Giemsa/Diff-Quik staining is intended 10% neutral buffered formalin — standard fixative for histopathology tissue biopsies Immunohistochemistry (IHC) Stains by Tumor Type Carcinomas (general) Cytokeratin (CK) markers — confirms epithelial origin Lymphomas CD45 (leukocyte common antigen) CD20 (B-cells) CD3 (T-cells) CD30 (Hodgkin/Reed-Sternberg cells) CD15 Breast cancer Estrogen receptor (ER) Progesterone receptor (PR) HER2/neu Ki-67 (proliferation index) Neuroendocrine tumors Chromogranin A Synaptophysin CD56 Sarcomas / mesenchymal tumors Vimentin Melanoma S-100 HMB-45 Melan-A Prostate cancer PSA (prostate-specific antigen) PSAP Germ cell tumors AFP — yolk sac tumor β-hCG — choriocarcinoma PLAP and OCT4 — seminoma/dysgerminoma --- Topic-Wise Predictions by Organ System This section predicts likely question chains — the way examiners typically pair a diagnosis question with a follow-up on complications, risk factors, or confirmatory tests for that same condition. Respiratory System Bronchiectasis Likely question chain: identify the condition → list predisposing/causative factors → list complications Predisposing factors: cystic fibrosis, recurrent childhood respiratory infections, bronchial obstruction (tumor, foreign body), ciliary dyskinesia, tuberculosis Complications: recurrent infections, haemoptysis, lung abscess, cor pulmonale, amyloidosis (secondary, AA type) Lung carcinoma Likely question chain: identify histological type from gross/microscopic appearance → risk factors → paraneoplastic syndromes Risk factors: smoking, asbestos exposure, radon exposure, occupational carcinogens Histological types: squamous cell carcinoma (central, cavitating), adenocarcinoma (peripheral, most common in non-smokers), small cell carcinoma (central, aggressive, paraneoplastic association), large cell carcinoma Tuberculosis Likely question chain: identify granuloma on histology → describe morphology → confirmatory stain/test Morphology: caseating granuloma with central necrosis, epithelioid histiocytes, Langhans giant cells, lymphocytic cuffing Confirmatory stain: Ziehl-Neelsen stain for acid-fast bacilli Cardiovascular System Myocardial infarction Likely question chain: identify gross/microscopic finding by time interval → complications → laboratory markers Complications: arrhythmia, cardiac rupture, papillary muscle rupture, mural thrombus, aneurysm, heart failure Laboratory markers: troponin I/T (most specific), CK-MB, myoglobin (earliest but non-specific) Atherosclerosis Likely question chain: identify the lesion → risk factors → complications Risk factors: hypertension, diabetes, smoking, hyperlipidaemia, obesity, family history Complications: thrombosis, embolism, aneurysm formation, ischaemia/infarction of downstream organs Gastrointestinal System Peptic ulcer disease Likely question chain: identify ulcer on specimen → causes → complications Causes: Helicobacter pylori infection, NSAID use, Zollinger-Ellison syndrome Complications: haemorrhage, perforation, obstruction, malignant transformation (gastric ulcers) Colorectal carcinoma Likely question chain: identify gross appearance → risk factors → tumor markers Risk factors: familial adenomatous polyposis, hereditary non-polyposis colorectal cancer (Lynch syndrome), inflammatory bowel disease, low-fibre diet, adenomatous polyps Tumor marker: carcinoembryonic