Master Pathology
for PMDC NLE Step 1

Core Concepts

Pathology is the study of disease: its etiology, pathogenesis, morphological changes, and clinical manifestations.

• Cell Injury & Adaptation:
  • Reversible: Cellular swelling, fatty change.
  • Irreversible (Necrosis): Coagulative, Liquefactive, Caseous, Fat, Fibrinoid, Gangrenous. Apoptosis (programmed cell death, no inflammation).
  • Adaptations: Hypertrophy, Hyperplasia, Atrophy, Metaplasia, Dysplasia.
• Inflammation & Repair:
  • Acute: Neutrophils, vascular changes (vasodilation, permeability). Mediators: Histamine, Prostaglandins, Leukotrienes.
  • Chronic: Macrophages, lymphocytes, plasma cells. Granulomatous inflammation (epithelioid macrophages, giant cells).
  • Repair: Regeneration vs. Fibrosis/Scar (granulation tissue). Key factor: TGF-β.
• Hemodynamics:
  • Edema: Increased hydrostatic P, decreased oncotic P, lymphatic obstruction.
  • Thrombosis: Virchow's Triad (endothelial injury, stasis, hypercoagulability).
  • Embolism: Thromboembolism (PE), Fat, Air, Amniotic fluid.
  • Infarction: Ischemic necrosis. Red (venous occlusion) vs. White (arterial occlusion).
  • Shock: Cardiogenic, Hypovolemic, Septic, Anaphylactic, Neurogenic.
• Neoplasia:
  • Benign vs. Malignant: Differentiation, growth, invasion, metastasis.
  • Carcinogenesis: Oncogenes (gain-of-function, e.g., RAS), Tumor Suppressor Genes (loss-of-function, e.g., P53, RB).
  • Metastasis: Lymphatic, Hematogenous, Seeding.
  • Grading (differentiation) vs. Staging (TNM, extent of spread).
• Immunopathology & Genetics:
  • Hypersensitivity: Type I (IgE), II (Abs to cell), III (Immune Complex), IV (T-cell mediated).
  • Autoimmunity: Loss of self-tolerance.
  • Immunodeficiency: Primary (congenital) vs. Secondary (acquired, e.g., HIV).
  • Genetic Disorders: Mendelian, Chromosomal, Multifactorial.

Clinical Presentation

Pathological processes manifest variably based on type, severity, and organ system. Common signs/symptoms include:

• Inflammation/Infection: Fever, pain, redness, swelling, organ dysfunction.
• Neoplasia: Masses, weight loss, fatigue, paraneoplastic syndromes.
• Ischemia/Infarction: Acute pain, organ failure.
• Genetic Disorders: Developmental anomalies, systemic dysfunctions.
• Immunological Disorders: Allergic reactions, autoimmune flare-ups, recurrent infections.
• General: Fatigue, weakness, unexplained weight changes.

Diagnosis (Gold Standard)

Histopathological Examination of tissue biopsies/resections is the gold standard for many diseases (e.g., neoplasia, inflammatory).

• Process: Gross & microscopic examination (H&E stain).
• Ancillary Studies:
  • Immunohistochemistry (IHC): Detects specific antigens.
  • Molecular Diagnostics: PCR, FISH, gene sequencing for mutations.
  • Cytopathology: Examination of exfoliated cells (e.g., Pap smear).

Other tools (imaging, labs) support diagnosis; histopathology confirms.

Management (First Line)

Management is disease-specific, but general principles for pathological processes include:

• Eradicating/Removing Cause: Antibiotics (infections), surgery/chemo/radiation (tumors), foreign body removal.
• Controlling Immune/Inflammatory Responses: NSAIDs, corticosteroids, immunosuppressants.
• Restoring Hemodynamic Balance: Fluid resuscitation (shock), anticoagulation (thrombosis).
• Supportive Care: Pain management, nutritional support, organ support.
• Genetic Counseling/Symptomatic Treatment: For incurable genetic disorders.

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