WHAT IS PATHOLOGY?
Pathology is a branch of medicine that answers four questions:
First: Why there is disease, i.e. what is the cause or etiology of a disease? The disease is due to microbes, virus, nutritional imbalance, genetic derangement, radiation, etc. Disease may also occur without any cause known as idiopathic or unknown origin.
Second: What are the changes in the cells or tissue or organs that is known as pathogenesis. This change may be morphological or naked eye or macroscopic change like cellular or tissue swelling, or microscopical, including ultrastructural change in cell structure or organelles.
Third: What is the prognosis or outcome of the disease? What are the after effects of the disease? What are the complications of a disease? If untreated an acute appendicitis may lead to burst appendix, perforation leading to peritonitis, formation of lump or abscess.
Fourth: What is the best management or treatment plan and after effect of treatment. If it is fully cured or there is relapse or not responds to treatment because of diverse etiology or atypical presentation.
Pathology is also the bridge between basic science and clinical practice. The physician depends on different branches of Pathology for exact diagnosis apart from clinical and other examination. These informations are provided by the Pathologist.
MECHANISM OF DISEASE
Sequence of events in response of cells/tissues to the etiological agent leads to morphological and structural changes. Structural alterations induced in cell/tissues, characteristic of the disease and leads to detection of the cause. Functional consequences of disease or morphological change and chemical alteration in patients influence the normal function and determine the clinical presentation, i.e. signs and symptoms, course of the disease and prognosis.
The word ‘Pathology’ is derived from Greek word Pathos meaning ‘Suffering’ and Logos meaning ‘Study’. So literally, (definition) pathology is the study of suffering.
Health: Health is a state of complete physical, mental and social well-being and not merely an absence of disease or infirmity.
Disease: A condition in which body health is impaired, a departure from a state of health, an alteration of the human body interrupting the performance of vital functions. Literally disease means (dis = Not ease; well-being, comfort) not feeling well, comfortable. That is disease is opposite to health, i.e. feeling not healthy is disease.
Lesion: Characteristic changes in the cells and tissues produced by disease in an individual or experimental animal.
Pathology is divided broadly into two main branches:
- General pathology: Basic reaction of cells and tissues to abnormal stimuli that underlie all diseases.
- Systemic pathology: Specific response of specialized organs or tissues to more or less well-defined stimuli.
Histopathology or anatomic pathology or morbid anatomy: One of the most common method of diagnosing disease. It is the study of tissues or organs and cells and it has three main subtypes:
- Surgical pathology: It is the study of tissue/organ removed from living body.
- Forensic pathology or autopsy: Study of organ/tissue removed from dead body or postmortem.
- Cytopathology: It is the study of cells either from exfoliative (shedding of cells in body cavities/fluids/secretions), fine needle aspiration cytology (FNAC) of superficial or deep lesions for diagnosis, imprint from fresh unfixed tissue imprint cytology.
There are some other special branches of pathology like:
Hematology—It means study of diseases of blood.
Molecular pathology—Which detects and diagnoses the abnormality in DNA level of cell by different techniques.
Some important milestone in the development of pathology and medicine:
- Cornelius Celsus (53 BC–7 AD): Described the cardinal signs of inflammation (redness, heat, swelling, pain).
- Hippocrates (460-377 BC): Greek born genius clinician. Recognized as father of medicine. He introduced ethical aspects of medicine.
- Marcello Malpighi (1624-1694): Regarded as father of histology. Described malpighian layer of skin, malpighian corpuscles in spleen, presence of capillaries.
- Antoni van Leeuwenhoek (1632-1723): Termed as Father of microbiology. He grinded fine lenses through which he looked various objects. He first described the protozoan giardia, RBC, spermatozoa and discovered many types of bacteria.
- Rudolf Virchow (1821-1905): Regarded as father of cellular pathology. Described etiology of embolism (Virchow's triad), metastasis of spread of tumors (Virchow's lymph node), leukemia. Introduced histopathology as diagnostic branch.
- Robert Koch (1843-1910): Koch's postulate, discovered tubercle and cholera bacilli.
- Karl Landsteiner, (1863-1943): Described human blood groups in 1901.
- Georgios Nicholas Papanicolaou (1883-1962): Greek born American Pathologist regarded as father of exfoliative cytology. He developed Pap's stain by which the cytological diagnosis of uterine cervix cancer was done in 1930 and other different body fluids are made.
- Sir William Leishman, (1865-1926): Leishman stain for blood and LD bodies are made.
- Tijo and Levan (1956): Identify chromosome and correct number (46).
- Kary Mullis (1983): Introduced polymerase chain reaction (PCR).
- NIH, US and Wellcome Trust (2000): Mapping of human genome with approximately 80000 gene.
- Ian Wilmut (1997): Cloned Sheep Dolly
- Ian Wilmut (2004): Therapeutic cloning of human embryo for motor neuron disease, e.g. human stem cell research.