Pathology
Introduction to Pathology
Introduction to pathology for MBBS: aetiology, pathogenesis, morphology and clinical significance, the role of the pathologist and key definitions, mapped to NMC codes PA1.1 to PA1.3.
MedNext Academy | 3 min read
Introduction to Pathology
Introduction to pathology for MBBS: aetiology, pathogenesis, morphology and clinical significance, the role of the pathologist and key definitions, mapped to NMC codes PA1.1 to PA1.3.
This introductory chapter defines what pathology is and how it underpins every clinical discipline. It sets out the four building blocks of any disease process, aetiology, pathogenesis, morphology and clinical significance, and describes the diagnostic role of the pathologist and the historical evolution of the subject.
High-yield: Introduction to Pathology
- Pathology is the study of disease, covering its cause (aetiology), mechanism (pathogenesis), structural change (morphology) and the resulting clinical effects.
- The four core aspects examiners ask are aetiology, pathogenesis, morphological changes and functional or clinical significance.
- Aetiology is the cause of a disease, while pathogenesis is the sequence of events by which that cause produces the disease.
- Morphological changes are the structural alterations in cells and tissues that are characteristic of a disease and used for diagnosis.
- Gross pathology studies changes visible to the naked eye; histopathology studies changes under the microscope.
- A lesion is any abnormal structural change in a tissue produced by disease.
- Idiopathic means a disease of unknown cause; iatrogenic means one caused by medical treatment.
- Aetiological factors are broadly genetic (intrinsic) or acquired (extrinsic, such as infections, chemicals, trauma and nutritional deficiency).
- The pathologist supports diagnosis through histopathology, cytology, haematology, clinical biochemistry and microbiology.
- Autopsy or post-mortem examination establishes the cause of death and provides quality feedback on clinical diagnosis.
- Rudolf Virchow proposed cellular pathology, placing the cell at the centre of disease, and is regarded as the father of modern pathology.
- Frozen section allows rapid intra-operative tissue diagnosis so the surgeon can decide the extent of an operation.
- Biopsy is the removal of tissue from a living patient for diagnosis; necropsy is examination after death.
- Immunohistochemistry uses antibodies against specific antigens to characterise tumours and guide targeted treatment.
- Molecular pathology detects gene mutations and rearrangements that refine diagnosis and predict response to therapy.
The four aspects of a disease process
- **Aetiology:** The cause: genetic (intrinsic) or acquired (infections, chemicals, physical agents, nutritional).
- **Pathogenesis:** The mechanism, the step-by-step sequence from cause to disease.
- **Morphology:** The structural changes, gross and microscopic, that allow diagnosis.
- **Clinical significance:** The functional consequences, signs, symptoms and course of the disease.
NMC competencies in this chapter
- **PA1.1:** Role of the pathologist in the diagnosis and management of disease
- **PA1.2:** Common definitions and terms used in pathology
- **PA1.3:** History and evolution of pathology
Frequently Asked Questions
What is the difference between aetiology and pathogenesis?
Aetiology is the cause of a disease, while pathogenesis is the sequence of events through which that cause leads to the disease and its structural changes.
What does a pathologist actually do?
A pathologist establishes and confirms diagnoses using histopathology, cytology, haematology, clinical biochemistry and microbiology, and guides treatment through techniques such as immunohistochemistry.
Who is considered the father of modern pathology?
Rudolf Virchow, who proposed cellular pathology and located the origin of disease in the cell rather than in the organ or the whole body.
Why is this chapter important for later subjects?
Every disease in medicine, surgery and the specialities is described using aetiology, pathogenesis, morphology and clinical significance, so a firm grip here makes the rest of pathology easier.
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