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For other uses, see Pathology (disambiguation).
Pathology is the study through examination of organs, tissues, cells and bodily fluids. The term encompasses both the medical specialty which uses tissues and body fluids to obtain clinically useful information, as well as the related scientific study of disease processes.
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The histories of both experimental and medical pathology can be traced to the earliest application of the scientific method to the field of medicine, a development which occurred in the Middle East during the Islamic Golden AgeToby E. Huff (2003), The Rise of Early Modern Science: Islam, China, and the West, p. 54, 246-247, 216-218. Cambridge University Press, ISBN 0521529948. and in Western Europe during the Italian Renaissance.[1] History of Pathology, at the USC School of Dentistry Most early pathologists were also practicing physicians or surgeons. Like other medical fields, pathology has become more specialized with time, and most pathologists today do not practice in other areas of medicine.
The concept of studying disease through the methodical dissection and examination of diseased bodies, organs, and tissues may seem obvious today, but there are few if any recorded examples of true autopsies performed prior to the second millennium west of India. Susrutha, the famous surgeon of Ayurveda, performed autopsies as early as 600 bc. Though the pathology of contagion was understood by Muslim physicians since the time of Avicenna (980–1037) who described it in The Canon of Medicine (c. 1020),Medicine And Health, "Rise and Spread of Islam 622-1500: Science, Technology, Health", World Eras, Thomson Gale. The Arabian physician Avenzoar (1091–1161), known to have made postmortem dissections, proved that the skin disease scabies was caused by a parasite, followed by Ibn al-Nafis (b. 1213) who used dissection to discover pulmonary circulation in 1242.Islamic medicine, Hutchinson Encyclopedia. In the 15th century, anatomic dissection was repeatedly used by the Italian physician Antonio Benivieni (1443-1502) to determine cause of death. Perhaps the most famous early gross pathologist was Giovanni Morgagni (1682-1771). His magnum opus, De Sedibus et Causis Morborum per Anatomem Indagatis, published in 1761, describes the findings of over 600 partial and complete autopsies, organised anatomically and methodically correlated with the symptoms exhibited by the patients prior to their demise. Although the study of normal anatomy was already well advanced at this date, De Sedibus was one of the first treatises specifically devoted to the corrolation of diseased anatomy with clinical illness.[2] A History of Medicine from the Biblioteca Centrale dell\'Area Biomedica[3] Founders of Modern Medicine: Giovanni Battista Morgagni. Medical Library and Historical Journal. 1903 October; 1(4): 270–277. By the late 1800s, an exhaustive body of literature had been produced on the gross anatomical findings characteristic of known diseases. The extent of gross pathology research in this period can be epitomized by the work of the Viennese pathologist (originally from Hradec Kralove in the Czech Rep.) Carl Rokitansky (1804-1878), who is said to have performed 20,000 autopsies, and supervised an additional 60,000, in his lifetime.[4] Karl von Rokitansky at Whonamedit.com
Rudolf Virchow (1821-1902) is generally recognized to be the father of microscopic pathology. While the compound microscope had been invented approximately 150 years prior, Virchow was one of the first prominent physicians to emphasize the study of manifestations of disease which were visible only at the cellular level.[5] Rudolf Virchow at Whonamedit.com A student of Virchow\'s, Julius Cohnheim (1839-1884) combined histology techniques with experimental manipulations to study inflammation, making him one of the earliest experimental pathologists. Cohnheim also pioneered the use of the frozen section procedure; a version of this technique is widely employed by modern pathologists to render diagnoses and provide other clinical information intraoperatively.[6] Jewish Encyclopedia entry on Julius Cohnheim
As new research techniques, such as electron microscopy, immunohistochemistry, and molecular biology have expanded the means by which biomedical scientists can study disease, the definition and boundaries of investigative pathology have become less distinct. In the broadest sense, nearly all research which links manifestations of disease to identifiable processes in cells, tissues, or organs can be considered experimental pathology.[7] Mission of the American Society for Investigative Pathology
Pathology is a broad and complex scientific field which seeks to understand the mechanisms of injury to cells and tissues, as well as the body\'s means of responding to and repairing injury. Disease processes may be incited or exacerbated by a variety of external and internal influences, including trauma, infection, poisoning, loss of blood flow, autoimmunity, inherited or acquired genetic damage, or errors of development. One common theme in pathology is the way in which the body\'s responses to injury, while evolved to protect health, can also contribute in some ways to disease processes.Ramzi Cotran, Vinay Kumar, Tucker Collins (1999). Robbins Pathologic Basis of Disease, Sixth Edition. W.B. Saunders. ISBN 072167335X. Elucidation of general principles underlying pathologic processes, such as cellular adaptation to injury, cell death, inflammation, tissue repair, and neoplasia, creates a conceptual framework with which to analyze and understand specific human diseases.
Cells and tissues may respond to injury and stress by specific mechanisms, which may vary according to the cell types and nature of the injury. In the short term, cells may activate specific genetic programs to protect their vital proteins and organelles from heat shock or hypoxia, and may activate DNA repair pathways to repair damage to chromosomes from radiation or chemicals. Hyperplasia is a long-term adaptive response of cell division and multiplication, which can increase the ability of a tissue to compensate for an injury. For example, repeated irritation to the skin can cause a protective thickening due to hyperplasia of the epidermis. Hypertrophy is an increase in the size of cells in a tissue in response to stress, an example being hypertrophy of muscle cells in the heart in response to increased resistance to blood flow as a result of narrowing of the heart\'s outflow valve. Metaplasia occurs when repeated damage to the cellular lining of an organ triggers its replacement by a different cell type.
Necrosis is the irreversible destruction of cells as a result of severe injury in a setting where the cell is unable to activate the needed metabolic pathways for survival or orderly degeneration. This is often due to external pathologic factors, such as toxins or loss of oxygen supply. Milder stresses may lead to a process called reversible cell injury, which mimics the cell swelling and vacuolization seen early in the necrotic process, but in which the cell is able to adapt and survive. In necrosis, the components of degenerating cells leak out, potentially contributing to inflammation and further damage. Apoptosis, in contrast, is a regulated, orderly degeneration of the cell which occurs in the settings of both injury and normal physiological processes.
A transmission electron microscope image of an immune cell crossing from the bone marrow into the circulation
Inflammation is a particularly important and complex reaction to tissue injury, and is particularly important in fighting infection. Acute inflammation is generally a non-specific response triggered by the injured tissue cells themselves, as well as specialized cells of the innate immune system and previously developed adaptive immune mechanisms. A localized acute inflammatory response triggers vascular changes in the injured area, recruits pathogen-fighting neutrophils, and begins the process of developing a new adaptive immune response. Chronic inflammation occurs when the acute response fails to entirely clear the inciting factor. While chronic inflammation can lay a positive role in containing a continuing infectious hazard, it can also lead to progressive tissue damage, as well as predisposing (in some cases) to the development of cancer.
Tissue repair, as seen in wound healing, is triggered by inflammation. The process may proceed even before the resolution of a precipitating insult, through the formation of granulation tissue. Healing involves the proliferation of connective tissue cells and blood vessel-forming cells as a result of hormonal growth signals. While healing is a critical adaptive response, an aberrant healing response can lead to progressive fibrosis, contractures, or other changes which can compromise function.
Neoplasia, or "new growth," is a proliferation of cells which is independent of any physiological process. The most familiar examples of neoplasia are benign tumors and cancers. Neoplasia results from genetic changes which cause cells to activate genetic programs inappropriately. Dysplasia is an early sign of a neoplastic process in a tissue, and is marked by persistence of immature, poorly differentiated cell forms. Interestingly, there are many similarities in the gene pathways activated in cancer cells, and those activated in cells involved in wound healing and inflammation.
Choristoma, ectopic tissue, heterotopic tissue, or aberrant tissue, is a mass of histologically normal tissue that is present in an abnormal location.MeSH classification C23.300.250 (pathological conditions, signs and symptoms
Physicians who practice pathology diagnose and characterize disease in living patients by examining biopsies and other specimens. For example, the vast majority of cancer diagnoses are made or confirmed by a pathologist. Pathologists may also conduct autopsies to investigate causes of death. The medical practice of pathology grew out the tradition of investigative pathology, and many of the academic leaders in pathology today are accomplished in both basic science research and diagnostic practice. However, as with other specialties in medicine, most modern physician-pathologists are employed in full-time practice, and do not perform original research.
Pathology is a unique medical specialty in that pathologists typically do not see patients directly, but rather serve as consultants to other physicians (often referred to as "clinicians" within the pathology community). However, in the United States and in many other countries, pathologists receive the same doctorate training, and undergo the same medical licensure process as other physicians. Pathology is a diverse field, and the organization of subspecialties within pathology vary between nations.
This mastectomy specimen contains an infiltrating ductal carcinoma of the breast. A pathologist will use immunohistochemistry and fluorescent in-situ hybridization to detect markers which determine the optimal chemotherapy regimen for this patient.
Anatomical pathologists diagnose disease and gain other clinically significant information through the examination of tissues and cells. This generally involves gross and microscopic visual examination of tissues, with special stains and immunohistochemistry employed to visualize specific proteins and other substances in and around cells. More recently, anatomical pathologists have begun to employ molecular biology techniques to gain additional clinical information from these same specimens. Anatomic pathologists serve as the definitive diagnosticians for most cancers, as well as numerous other diseases.
Pathogenic organisms are grown from patient specimens in clinical microbiology labs, allowing selection of the correct antibiotics
Clinical pathology, also known as laboratory medicine, is the medical specialty concerned with diagnosing diseases based on the analysis of body fluids, such as plasma, urine, stool, respiratory or mucosal secretions, inflammatory exudates, and pleural, pericardial, peritoneal, synovial, or cerebrospinal fluid. The practice of clinical pathology is centered around the clinical laboratory. In modern clinical laboratories, many routine studies are largely automated. The clinical pathologist is responsible for overseeing the work of laboratory technicians, performing quality assurance to assure the validity of test results, performing interpretations of more complex studies, and serving as a consultant to clinicians so that the most appropriate studies can be performed for the diagnosis or assessment of an individual patient\'s condition. In some areas, non-pathologists, such as other physicians or Ph.D.\'s may run clinical labs and perform functions within those specific labs which are similar to the role of a board-certified clinical pathologist.
Sub-specialties within clinical pathology include the following:
In the United States, subspecialty-trained doctors of dentistry, rather than medical doctors, can be certified by a professional board to practice Oral and Maxillofacial Pathology.
In the United States, pathologists are allopathic (MD, MBBS, MBChB, etc.) or osteopathic (DO) physicians, that have completed a four-year undergraduate program, four years of medical school training, and three to four years of postgraduate training in the form of a pathology residency. Training may be within two primary specialties, as recognized by the American Board of Pathology: Anatomic Pathology, and Clinical Pathology, each of which requires separate board certification. Many pathologists seek a broad-based training and become certified in both fields. These skills are complementary in many hospital-based private practice settings, since the day-to-day work of many clinical laboratories only requires the intermittent attention of a physician. Thus, pathologists are able to spend much of their time evaluating anatomic pathology cases, while remaining available to cover any special issues which might arise in the clinical laboratories. Pathologists may pursue specialised fellowship training within one or more sub-specialties of either anatomic or clinical pathology. Some of these sub-specialities permit additional board certification, while others do not.[8] Homepage of the American Board of Pathology
In the UK pathologists are medical doctors registered with the UK General Medical Council. They will have completed an undergraduate medical education which in most countries lasts 4-6 years. The training to become a pathologist is under the oversight of the Royal College of Pathologists. Typically a one year training attachment is followed by an aptitude test. This is followed by further specialist training in surgical pathology, cytopathology, and post mortem pathology. There are two examinations run by the Royal College of Pathologists termed Part 1 and Part 2. The Part 2 examination is designed to test competence to work as an independent practitioner in pathology and is typically taken after 5 years specialist training. All post-graduate medical training and education in the UK is overseen by the Postgraduate Medical Education and Training Board. It is possible to take a specialist part 2 examination in paediatric pathology or neuropathology. It is possible to take a special diploma in dermatopathology or cytopathology, recognising additional specialist training and expertise.
Veterinary pathologists are veterinary practitioners who specialise in the diagnosis and characterization of veterinary diseases through the examination of animal tissue and body fluids. Veterinary pathologists are veterinarians with advanced training (board certification or Ph.D.) in either diagnostic pathology or research into the biological processes underlying disease (pathobiology). Diagnostic veterinary pathologists are further subcategorized as either anatomical pathologists or clinical pathologists. Clinical pathologists examine specimens such as blood, excretions or biopsy material to diagnose disease in living animals. Anatomical pathologists utilize post mortem examinations of dead animals to arrive at a diagnosis. Post mortem examinations entail a necropsy (an animal autopsy), histopathologic (microscopic) study of tissue specimens collected at the necropsy and sometimes specialized studies (radiographic, toxicologic, etc.)Veterinary Pathologist: Training - the Royal College of Pathologists.
Plant pathologists are specialized scientists who investigate the causes of diseases in plants.
As in every field, specialized software exists: the idea being to maintain Electronic medical record or Electronic health record
| Pathology | |
|---|---|
| Principles of pathology | Disease - Necrosis - Infection - Ischemia - Inflammation - Wound healing - Neoplasia |
| Anatomical pathology | Surgical pathology - Cytopathology - Autopsy - Molecular pathology - Forensic pathology - Dental pathology Gross examination - Histopathology - Immunohistochemistry - Electron microscopy - Immunofluorescence - Fluorescent in situ hybridization |
| Clinical pathology | Clinical chemistry - Hematopathology - Transfusion medicine - Medical microbiology - Diagnostic immunology Enzyme assay - Mass spectrometry - Chromatography - Flow cytometry - Blood bank - Microbiological culture - Serology |
| Health science > Medicine | |||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Specialties and Subspecialties |
| ||||||||||||||||
| Other |
Allopathic medicine · Epidemiology · History of medicine · Hospital medicine · Medical education · Medical genetics · Medical school · Osteopathic medicine · Pharmacy · Physician (M.D. and D.O.) · Physician Assistant · Public health · Sports medicine | ||||||||||||||||
| Major subfields of biology |
|---|
| Anatomy - Astrobiology - Biochemistry - Bioinformatics - Biostatistics - Botany - Cell biology - Ecology - Developmental biology - Epidemiology - Evolutionary biology - Genetics - Genomics - Immunology - Marine biology - Human biology - Microbiology - Molecular biology - Neuroscience - Nutrition - Origin of life - Paleontology - Parasitology - Pathology - Physiology - Systems biology - Taxonomy - Zoology |
| Pathology: Cancer, Tumors, Neoplasms, and oncology (C00-D48, 140-239) | |
|---|---|
| Benign tumors | Hyperplasia - Cyst - Pseudocyst - Hamartoma - Benign tumor |
| Malignant progression | Dysplasia - Carcinoma in situ - Cancer - Metastasis |
| Topography | lip, oral cavity and pharynx: Oral - Head/Neck - Nasopharyngeal
digestive system: tract (Esophagus, Stomach, Small intestine, Colon/rectum, Appendix, Anus) - glands (Liver, Bile duct, Gallbladder, Pancreas) respiratory system: Larynx - Lung bone, articular cartilage, skin, and connective tissue: Bone - Skin - Blood urogenital: breast and female genital organs (Breast, Vagina, Cervix, Uterus, Endometrium, Ovaries) - male genital organs (Penis, Prostate, Testicles) - urinary organs (Kidney, Bladder) nervous system: Eye (Uvea) - Brain endocrine system: Thyroid (Papillary, Follicular, Medullary, Anaplastic) - Adrenal tumor (Adrenocortical carcinoma, Pheochromocytoma) - Pituitary |
| Misc. | Tumor suppressor genes/oncogenes - Staging/grading - Carcinogenesis - Carcinogen - Research - Paraneoplastic syndrome - List of oncology-related terms |
| Pathology: hematology (primarily D50-D77, 280-289) | |
|---|---|
| RBCs/anemia/ hemoglobinopathy (Myeloid) | nutritional anemia: Iron deficiency anemia, Plummer-Vinson syndrome, Megaloblastic anemia (Pernicious anemia) hereditary hemolytic anemia: G6PD Deficiency, Thalassemia, Sickle-cell disease/trait, Hereditary spherocytosis, Hereditary elliptocytosis, Hereditary stomatocytosis acquired hemolytic anemia: Autoimmune (Warm), HUS, MAHA, PNH, PCH aplastic anemia: Acquired PRCA, Diamond-Blackfan anemia, Fanconi anemia • Sideroblastic anemia • Hemochromatosis |
| Coagulation/platelets (Myeloid) | coagulopathy: DIC (Congenital afibrinogenemia, Purpura fulminans) • Hemophilia (A/VII, B/IX, C/XI, XIII) • Von Willebrand disease
Purpura: Henoch-Schönlein, ITP (Evans syndrome), TTP primary hypercoagulable state: Protein C deficiency - Protein S deficiency - Antithrombin III deficiency - Factor V Leiden - Activated protein C resistance - Antiphospholipid syndrome other hemorrhagic conditions: Bernard-Soulier syndrome - Glanzmann\'s thrombasthenia - Grey platelet syndrome - May Hegglin anomaly Essential thrombocytosis - Thrombocytopenia |
| Monocytes/Macrophages (Myeloid) | WHO-I histiocytosis (Langerhans cell histiocytosis)
WHO-II/non-Langerhans-cell histiocytosis (Juvenile xanthogranuloma, Hemophagocytic lymphohistiocytosis) WHO-III/malignant histiocytic disorders (Acute monocytic leukemia, Malignant histiocytosis, Erdheim-Chester disease) -penia: Monocytopenia |
| Granulocytes (Myeloid) | -cytosis: granulocytosis (Neutrophilia, Eosinophilia, Basophilia) -penia: Granulocytopenia/agranulocytosis (Neutropenia, Kostmann syndrome) |
| Other/general myeloid | Chronic granulomatous disease |
| Lymphoid | -cytosis: Lymphocytosis -penia: Lymphopenia |
| Other | Asplenia/hyposplenism - Methemoglobinemia - Pancytopenia |
| See also hematological malignancy and immune disorders | |
| Endocrine pathology: endocrine diseases (E00-35, 240-259) | |
|---|---|
| Thyroid | Hypothyroidism (Iodine deficiency, Cretinism, Congenital hypothyroidism, Goitre, Myxedema) - Hyperthyroidism (Graves disease, Toxic multinodular goitre, Teratoma with thyroid tissue or Struma ovarii) - Thyroiditis (De Quervain\'s thyroiditis, Hashimoto\'s thyroiditis, Riedel\'s thyroiditis) - Euthyroid sick syndrome |
| Pancreas | Diabetes mellitus (type 1, type 2, coma, angiopathy, ketoacidosis, nephropathy, neuropathy, retinopathy) - Hypoglycemia - Hyperinsulinism - Zollinger-Ellison syndrome - insulin receptor (Rabson-Mendenhall syndrome) |
| Parathyroid | Hypoparathyroidism (Pseudohypoparathyroidism) - Hyperparathyroidism (Primary, Secondary, Tertiary) |
| Pituitary | Hyperpituitarism (Acromegaly, Hyperprolactinaemia, SIADH) - Hypopituitarism (Simmonds\' disease/Sheehan\'s syndrome, Kallmann syndrome, Growth hormone deficiency, Diabetes insipidus) - Adiposogenital dystrophy - Empty sella syndrome |
| Adrenal | Cushing\'s syndrome (Nelson\'s syndrome, Pseudo-Cushing\'s syndrome) - CAH (due to 21-hydroxylase deficiency) - Hyperaldosteronism (Conn syndrome, Bartter syndrome) - Adrenal insufficiency (Addison\'s disease) - Hypoaldosteronism |
| Gonads | ovarian dysfunction (Polycystic ovary syndrome, Premature ovarian failure) - testicular dysfunction (5-alpha-reductase deficiency) - testosterone biosynthesis (17-beta-hydroxysteroid dehydrogenase deficiency) - general (Hypogonadism, Delayed puberty, Precocious puberty) |
| Other | Autoimmune polyendocrine syndrome - Carcinoid syndrome - Short stature (Laron syndrome, Psychogenic dwarfism) - Gigantism - Androgen insensitivity syndrome - Progeria - Multiple endocrine neoplasia (1, 2) |
| Nutritional pathology (E40-68, 260-269) | |
|---|---|
| Malnutrition | Kwashiorkor - Marasmus - Catabolysis |
| Avitaminosis | B vitamins: B1: Beriberi/Wernicke\'s encephalopathy, B2: Ariboflavinosis, B3: Pellagra, B6: Pyridoxine deficiency, B7: Biotin deficiency, B9: Folate deficiency, B12: Vitamin B12 deficiency other vitamins: A: Vitamin A deficiency/Bitot\'s spots, C: Scurvy, D: Rickets/Osteomalacia |
| Mineral deficiency | Zinc deficiency - Iron deficiency - Magnesium deficiency - Chromium deficiency |
| Hyperalimentation | Obesity - Vitamin poisoning (Hypervitaminosis A, Hypervitaminosis D) |
| Metabolic pathology / Inborn error of metabolism (E70-90, 270-279) | |
|---|---|
| Amino acid | Aromatic (Phenylketonuria, Alkaptonuria, Ochronosis, Tyrosinemia, Albinism, Histidinemia) - Branched-chain Organic acidemias (Maple syrup urine disease, Propionic acidemia, Methylmalonic acidemia, Isovaleric acidemia, 3-Methylcrotonyl-CoA carboxylase deficiency), IBD deficiency - Straight-chain (Hyperlysinemia, Pipecolic acidemia, Saccharopinuria) - Transport (Cystinuria, Cystinosis, Hartnup disease, Fanconi syndrome, Oculocerebrorenal syndrome, Lysinuric protein intolerance) - Sulfur (Cystathioninuria, Hawkinsinuria, Homocystinuria, Hypermethioninemia) - Urea cycle disorder (N-Acetylglutamate synthase deficiency, Carbamoyl phosphate synthetase I deficiency, Ornithine transcarbamylase deficiency/translocase deficiency, Citrullinemia, Argininosuccinic aciduria, Argininemia, Hyperammonemia) - Glutaric acidemia type 1, type 2 - Hyperprolinemia - Prolidase deficiency - Sarcosinemia - Other Beta-ketothiolase deficiency - Glutathione synthetase deficiency - Glycine encephalopathy - GAMT deficiency - Tetrahydrobiopterin deficiency - Trimethylaminuria |
| Carbohydrate | Lactose intolerance - Glycogen storage disease (type I, type II, type III, type IV, type V, type VI, type VII) - fructose metabolism (Fructose intolerance, Fructose bisphosphatase deficiency, Essential fructosuria) - galactose metabolism (Galactosemia, Galactose-1-phosphate uridylyltransferase galactosemia, Galactokinase deficiency) - other intestinal carbohydrate absorption (Glucose-galactose malabsorption, Sucrose intolerance) - pyruvate metabolism and gluconeogenesis (PCD, PDHA) - Pentosuria - Renal glycosuria |
| Lipid storage | Sphingolipidoses/Gangliosidoses: GM2 gangliosidoses (AB variant, Sandhoff disease, Tay-Sachs disease) - GM1 gangliosidoses - Mucolipidosis type IV - Gaucher\'s disease - Niemann-Pick disease - Farber disease - Fabry\'s disease - Metachromatic leukodystrophy - Krabbe disease Neuronal ceroid lipofuscinosis (Batten disease) - Cerebrotendineous xanthomatosis - Cholesteryl ester storage disease (Wolman disease) |
| Fatty acid metabolism | Lipoprotein/lipidemias: Hyperlipidemia - Hypercholesterolemia - Familial hypercholesterolemia - Xanthoma - Combined hyperlipidemia - Lecithin cholesterol acyltransferase deficiency - Tangier disease - Abetalipoproteinemia - Smith-Lemli-Opitz syndrome Cholesterol biosynthesis: Mevalonic aciduria Fatty acid: Adrenoleukodystrophy, |
