Two pathologists view a tissue sample attempting to determine if it contains cancerous cells.
|Subdivisions||Anatomical, clinical, dermatologic, forensic, molecular, haematological|
|Significant diseases||Macroscopic and microscopic diseases|
|Significant tests||Dissection, microscopy|
Pathology is the causal study and diagnosis of disease. The word pathology is from Ancient Greek πάθος, pathos which may be translated into English as either "experience" or "suffering", and -λογία, -logia, "an account of" or "the study of". Pathologization. Pathologies (or pathoses) are terms which refer to the predicted or actual progression of diseases. The prefix path is sometimes used to indicate a state of disease, and may be used to indicate physical disease (e.g. cardiomyopathy) or psychological condition (e.g. psychopath) . A physician practicing pathology is called a pathologist.
Pathology addresses four components of disease: cause/etiology, mechanisms of development (pathogenesis), structural alterations of cells (morphologic changes), and the consequences of changes (clinical manifestations).Medical practice and research have numerous notable subdivisions based on either the system being studied, as with dermatopathology or the focus of the examination, such as forensic pathology, a specialty focused upon determining cause of death, post-mortem.
- 1 History
- 2 General medical and research pathology
- 3 Systems-specific fields
- 4 Other medical fields
- 5 Psychopathology
- 6 The Study of pathology in non-humans
- 7 See also
- 8 References
- 9 External links
The study of pathology, including the detailed examination of the body, including dissection and inquiry into specific maladies, dates back to antiquity. Rudimentary understanding of many conditions was present in most early societies and is attested to in the records of the earliest historical societies, including those of the Middle East, India, and China.  By the Hellenic period of ancient Greece, a concerted causal study of disease was underway (see Medicine in ancient Greece, with many notable early physicians (such as Hypocrates, for whom the modern Hypocratic oath is named) having developed methods of diagnosis and prognosis for a number of diseases. The medical practices of the Romans and those of the Byzantines continued from these Greek roots, but, as with many areas of scientific inquiry, growth in understanding of medicine stagnated some after the Classical Era, but continued to slowly develop throughout numerous cultures. Notably, many advances were made in the medieval era of Islam (see Medicine in medieval Islam), during which numerous texts of complex pathologies were developed, also based on the Greek tradition.  Even, so complex understanding of disease mostly languished until understanding again began to accelerate during the Renaissance, Enlightenment, and Baroque eras, during which the resurgence of the empirical method at new centers of scholarship. By the 17th century, the study of micrography was underway and examination of tissues had led British Royal Society member Robert Hooke to coin the word "cell", setting the stage for later germ theory.
Modern pathology began to develop as a distinct field of inquiry during the 19th Century through natural philosophers and physicians that studied disease and the informal study of what they termed “pathological anatomy” or “morbid anatomy”. However, pathology as a formal area of specialty was not fully developed until the late 19th and early 20th centuries, with the advent of detailed study of microbiology. In the 19th century, physicians had begun to understand that disease-causing pathogens, or "germs" (a catch-all for disease-causing, or pathogenic, microbes, such as bacteria, viruses, fungi, amoebae, molds, protists, and prions) existed and were capable of reproduction and multiplication, replacing earlier beliefs in humors or even spiritual agents, that had dominated for much of the previous 1,500 years in European medicine. With the new understanding of causative agents, physicians began to compare the characteristics of one germ’s symptoms as they developed within an affected individual to another germ’s characteristics and symptoms. This realization led to the foundational understanding that diseases are able to replicate themselves, and that they can have many profound and varied effects on the human host. In order to determine causes of diseases, medical experts used the most common and widely accepted assumptions or symptoms of their times, a general principal of approach that persists into modern medicine.
Modern medicine was particularly advanced by further developments of the microscope to analyze tissues, to which Rudolf Virchow gave a significant contribution, leading to a slew of research developments. By the late 1920s to early 1930s pathology was deemed a medical specialty. Combined with developments in the understanding of general physiology, by the beginning of the 20th century, the study of pathology had begun to split into a number of rarefied fields and resulting in the development of large number of modern specialties within pathology and related disciplines of diagnostic medicine.
General medical and research pathology
The modern practice of pathology is divided into a number of subdisciplines within the discreet but deeply interconnected aims of biological research and medical practice. Biomedical research into disease incorporates the work of vast variety of life science specialists, wheras, in most parts of the world, to be licensed to practice pathology as medical specialty, one has to complete medical school and secure a license to practice medicine. Structurally, the study of disease is divided into many different fields which study or diagnose markers for disease using methods and technologies particular to specific scales, organs and tissue types.
Anatomical pathology (Commonwealth) or anatomic pathology (United States) is a medical specialty that is concerned with the diagnosis of disease based on the gross, microscopic, chemical, immunologic and molecular examination of organs, tissues, and whole bodies (as in a general examination or an autopsy). Anatomical pathology is itself divided into subfields, the main ones being surgical pathology, cytopathology, and forensic pathology. Anatomical pathology is one of two main divisions of the medical practice of pathology, the other being clinical pathology, the diagnosis of disease through the laboratory analysis of bodily fluids and tissues. Sometimes, pathologists practice both anatomical and clinical pathology, a combination known as general pathology.
Cytopathology (sometimes referred to as "cytology") is a branch of pathology that studies and diagnoses diseases on the cellular level. It is usually used to aid in the diagnosis of cancer, but also helps in the diagnosis of certain infectious diseases and other inflammatory conditions as well as thyroid lesions, diseases involving sterile body cavities (peritoneal, pleural, and cerebrospinal), and a wide range of other body sites. Cytopathology is generally used on samples of free cells or tissue fragments, in contrast to histopathology, which studies whole tissues and cytopathologic tests are sometimes called smear tests because the samples may be smeared across a glass microscope slide for subsequent staining and microscopic examination. However, cytology samples may be prepared in other ways, including cytocentrifugation. Different types of smear tests may also be used for cancer diagnosis. In this sense, it is termed a cytologic smear.
Forensic pathology focuses on determining the cause of death by examination of a corpse or partial remains. An autopsy is typically performed by a coroner or medical examiner, often during the criminal law investigations; in this role, Coroners and medical examiners are also frequently asked to confirm the identity of a corpse. The requirements for becoming a licensed practitioner of forensic pathology varies from country to country, but typically a minimal requirement is a medical doctorate with a specialty in general or anatomical pathology and subspecialty in forensic science who has completed specialist training in anatomical pathology and who has subsequently sub-specialized in forensic pathology. The methods utilized by forensic scientists to determine death includes examination of tissue specimens in order to identify the presence or absence of natural disease and other microscopic findings, interpretations of toxicologicology on body tissues and fluids to determine the chemical cause of overdoses, poisonings or other cases involving toxic agents, and the examinations of physical trauma. Forensic pathology is a major component in the trans-disciplinary field of Forensic science.
Surgical pathology is one of the primary areas of practice for most anatomical pathologists. Surgical pathology involves the gross and microscopic examination of surgical specimens, as well as biopsies submitted by surgeons and non-surgeons such as general internists, medical subspecialists, dermatologists, and interventional radiologists. Often an excised tissue sample is the best and most definitive evidence of disease (or lack thereof) in cases where tissue is surgically removed from a patient. These determinations are usually accomplished by a combination of gross (i.e., macroscopic) and histologic (i.e., microscopic) examination of the tissue, and may involve evaluations of molecular properties of the tissue by immunohistochemistry or other laboratory tests.
There are two major types of specimens submitted for surgical pathology analysis: biopsies and surgical resections. A biopsy is a small piece of tissue removed primarily for the purposes of surgical pathology analysis, most often in order to render a definitive diagnosis. Types of biopsies include core biopsies, which are obtained through the use of large-bore needles, sometimes under the guidance of radiological techniques such as ultrasound, CT scan, or magnetic resonance imaging. Incisional biopsies are obtained through diagnostic surgical procedures that remove part of a suspicious lesion, whereas excisional biopsies remove the entire lesion, and are similar to therapeutic surgical resections. Excisional biopsies of skin lesions and gastrointestinal polyps are very common. The pathologist's interpretation of a biopsy is critical to establishing the diagnosis of a benign or malignant tumor, and can differentiate between different types and grades of cancer, as well as determining the activity of specific molecular pathways in the tumor. Surgical resection specimens are obtained by the therapeutic surgical removal of an entire diseased area or organ (and occasionally multiple organs). These procedures are often intended as definitive surgical treatment of a disease in which the diagnosis is already known or strongly suspected, but pathological analysis of these specimens remains important in confirming the previous diagnosis.
Clinical pathology is a medical specialty that is concerned with the diagnosis of disease based on the laboratory analysis of bodily fluids such as blood and urine, as well as tissues, using the tools of chemistry, clinical microbiology, hematology and molecular pathology. Clinical pathologists work in close collaboration with medical technologists, hospital administrations, and referring physicians. Clinical pathology is one of the two major divisions of pathology, the other being anatomical pathology. Clinical pathologist learn to administer a number of visual and microscopic tests and an especially large variety of tests of the biophysical properties of tissue samples involving Automated analysers and cultures.
Hematopathology is the study of diseases of blood cells (including constituents such as white blood cells, red blood cells, and platelets)and the tissues, and organs comprising the hematopoietic system. The term hematopoietic system refers to tissues and organs that produce and/or
primarily host hematopoietic cells and include bone marrow, the lymph nodes, thymus, spleen, and other lymphoid tissues. In the United States, hematopathology is a board certified subspecialty (American Board of Pathology) practiced by those physicians who have completed general pathology residency (anatomic, clinical, or combined) and an additional year of fellowship training in hematology. The hematopathologist reviews biopsies of lymph nodes, bone marrows and other tissues involved by an infiltrate of cells of the hematopoietic system. In addition, the hematopathologist may be in charge of flow cytometric and/or molecular hematopathology studies.
Histopathology refers to the microscopic examination of various forms of human tissue. Specifically, in clinical medicine, histopathology refers to the examination of a biopsy or surgical specimen by a pathologist, after the specimen has been processed and histological sections have been placed onto glass slides. This contrasts with the methods of cytopathology which utilizes free cells or tissue fragments. Histopathological examination of tissues starts with surgery, biopsy, or autopsy. The tissue is removed from the body of an organism and then placed in a fixative which stabilizes the tissues to prevent decay. The most common fixative is formalin, although frozen section fixing is also common. To see the tissue under a microscope, the sections are stained with one or more pigments. The aim of staining is to reveal cellular components; counterstains are used to provide contrast. Histochemistry refers to the science of using chemical reactions between laboratory chemicals and components within tissue. The histological slides are then interpreted diagnostically and the resulting pathology report describes the histological findings and the opinion of the pathologist. In the case of cancer, this represents the tissue diagnosis required for most treatment protocols.
Molecular pathology is focused upon the study and diagnosis of disease through the examination of molecules within organs, tissues or bodily fluids. Molecular pathology is multidisciplinary by nature and shares some aspects of practice with both anatomic pathology and clinical pathology, molecular biology, biochemistry, proteomics and genetics. It is often applied in a context that is as much scientific as directly medical and encompasses the development of molecular and genetic approaches to the diagnosis and classification of human diseases, the design and validation of predictive biomarkers for treatment response and disease progression, and the susceptibility of individuals of different genetic constitution to develop disorders. The crossover between molecular pathology and epidemiology is represented by a related field "molecular pathological epidemiology".  Molecular pathology is commonly used in diagnosis of cancer and infectious diseases. Techniques are numerous but include quantitative polymerase chain reaction (qPCR), multiplex PCR, DNA microarray, in situ hybridization, DNA sequencing, antibody based immunofluorescence tissue assays, molecular profiling of pathogens, and analysis of bacterial genes for antimicrobial resistance.
Medical training and accreditation
Individual nations vary some in the medical licensing required of pathologists. In the United States, pathologists are physicians (D.O. or M.D.) 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: anatomical Pathology and clinical Pathology, each of which requires separate board certification. The American Osteopathic Board of Pathology also recognizes four primary specialties: anatomic pathology, dermatopathology, forensic pathology, and laboratory medicine. Pathologists may pursue specialised fellowship training within one or more subspecialties of either anatomical or clinical pathology. Some of these subspecialties permit additional board certification, while others do not.
In the United Kingdom, pathologists are medical doctors licensed by the UK General Medical Council. The training to become a pathologist is under the oversight of the Royal College of Pathologists. After four to six years of undergraduate medical study, trainees proceed to a two year foundation program. Full-time training in histopathology currently lasts between five and five and a half years and includes specialist training in surgical pathology, cytopathology, and autopsy pathology. It is also possible to take a Royal College of Pathologists diploma in forensic pathology, dermatopathology, or cytopathology, recognising additional specialist training and expertise and to get specialist accreditation in forensic pathology, pediatric pathology, and neuropathology. All postgraduate medical training and education in the UK is overseen by the General Medical Council.
In France, Pathology is separate in two distinct specialties, anatomical pathology and clinical pathology. Residencies for both lasts four years. Residency in anatomical pathology is open to physicians only, while clinical pathology is open to both physicians and pharmacists. Anatomical pathology in France is integrated in the internal medicine specialty track. At the end of the second year of clinical pathology residency, residents can choose between general clinical pathology and a specialization in one of the disciplines, but they can not practice anatomical pathology, nor can anatomical pathology residents can not practice clinical pathology.
In addition the common divisions in medical specialties discussed above, a number of discreet subfields have developed which are particular to specific origins. Although researchers in these fields may come from a wide variety of medical and bioscience backgrounds, in medical contexts the actual diagnostic work on the tissues involved is often performed by the same anatomic or clinical pathologists described above. The information in this section mostly concerns pathology as it regards common medical practice in these systems, but each of the bellow specialties is also the subject of voluminous pathology research as regards the disease pathways of specific pathogens and disorders.
Dermatopathology is a subspecialty of anatomic pathology that focuses on the skin and the rest of the integumentary system as an organ. It is unique in that there are two routes which a physician can use to obtain thespecialization. All general pathologists and general dermatologists are trained in the pathology of the skin, so the term dermatopathologist denotes either of these who has reached a certainly level accreditation and experience; in the USA, either a general pathologist or a dermatologist can undergo a 1 to 2 year fellowship in the field of dermatopathology. The completion of this fellowship allows one to take a subspecialty board examination, and becomes a board certified dermatopathologist.
Dermatologists are able to recognize most skin diseases based on their appearances, anatomic distributions, and behavior. Sometimes, however, those criteria do not allow a conclusive diagnosis to be made, and a skin biopsy is taken to be examined under the microscope using usual histological tests. In some cases, additional specialized testing needs to be performed on biopsies, including immunofluorescence, immunohistochemistry, electron microscopy, flow cytometry, and molecular-pathologic analysis. One of the greatest challenges of dermatopathology is its scope. More than 1500 different disorders of the skin exist, including cutaneous eruptions ("rashes") and neoplasms. Therefore, dermatopathologists must maintain a broad base of knowledge in clinical dermatology, and be familiar with several other specialty areas in Medicine.
Neuropathology is the study of disease of nervous system tissue, usually in the form of either small surgical biopsies or sometimes whole brains in the case of autopsy. Neuropathology is a subspecialty of anatomic pathology, neurology, and neurosurgery. In many English speaking countries neuropathology is considered a subfield of anatomical pathology. In contrast, there are a number of independent university chairs in neuropathology and even institutes of neuropathology in German speaking countries due to a different historical background. A physician who specializes in neuropathology, usually by completing a fellowship after a residency in anatomical or general pathology, is called a neuropathologist. In day-to-day clinical practice, a neuropathologist is a consultant for other physicians. If a disease of the nervous system is suspected, and the diagnosis cannot be made by less invasive methods, a biopsy of nervous tissue is taken from the brain or spinal cord to aid in diagnosis. The biopsy is usually requested after a mass is detected by radiologic imaging. With autopsies, the principal work of the neuropathologist is to help in the post-mortem diagnosis of various conditions that affect the central nervous system. Biopsies can also consist of the skin. Epidermal nerve fiber density testing (ENFD) is a more recently developed neuropathology test in which a punch skin biopsy is taken to identify small fiber neuropathies by analyzing the nerve fibers of the skin. This pathology test is becoming available in select labs as well as many universities; it replaces the traditional nerve biopsy test as less invasive.
Oral and Maxillofacial Pathology
Oral and Maxillofacial Pathology is one of nine dental specialties recognized by the American Dental Association. Oral Pathologists must complete three years of post doctoral training in an accredited program and subsequently obtain Diplomate status from the American Board of Oral and Maxillofacial Pathology. The specialty focuses on the diagnosis, clinical management and investigation of diseases that affect the oral cavity and surrounding maxillofacial structures including but not limited to odontogenic, infectious, epithelial, salivary gland, bone and soft tissue pathologies. Although concerned with a broad variety of diseases of the oral cavity, they have roles distinct from otorhinolaryngologists ("ear, nose, and throat" specialists), and speech pathologists, the latter of which helps diagnose many neurological or neuromuscular conditions relevant to speech phonology or swallowing.
Pulmonary pathology is the subspecialty of surgical pathology which deals with the diagnosis and characterization of neoplastic and non-neoplastic diseases of the lungs and thoracic pleura. Diagnostic specimens are often obtained via bronchoscopic transbronchial biopsy, CT-guided percutaneous biopsy, or video-assisted thoracic surgery (VATS). The diagnosis of inflammatory or fibrotic diseases of the lungs is considered by many pathologists to be particularly challenging.
Renal pathology is a subspecialty of anatomic pathology that deals with the diagnosis and characterization of disease of the kidneys. In a medical setting, renal pathologists work closely with nephrologists and transplant surgeons, who typically obtain diagnostic specimens via percutaneous renal biopsy. The renal pathologist must synthesize findings from traditional microscope histology, electron microscopy, and immunofluorescence to obtain a definitive diagnosis. Medical renal diseases may affect the glomerulus, the tubules and interstitium, the vessels, or a combination of these compartments.
Other medical fields
Although separate fields in terms of medical practice, there are a number of areas of inquiry in medicine and medical science which either overlap greatly with general pathology, work in tandem with it, or which contribute significantly to the understanding of the pathology of a given disease or its course in an individual. As a significant portion of all general pathology practice is concerned with cancer, the practice oncology is deeply tied to, and dependent upon, the work of both anatomical and clinical pathologists. Biopsy, resection and blood tests are all essential for the diagnoses of many kinds of cancer and for the staging of an cancerous masses.
Medical imaging is the process of generating visual representations of the interior of a body for clinical analysis and medical intervention. Medical imaging seeks to reveal internal structures hidden by the skin and bones in order to plan appropriate treatment. Medical imaging also establishes a database of normal anatomy and physiology to make it possible to identify abnormalities. These techniques are often performed in combination with general pathology procedures and are themselves often essential to developing new understanding of the pathogenesis of a given disease and tracking the progress of disease in specific medical cases. Examples of important subdivisions in medical imaging include incorporates radiology which uses the imaging technologies of X-ray radiography, magnetic resonance imaging, medical ultrasonography or ultrasound, endoscopy, elastography, tactile imaging, thermography, medical photography, nuclear medicine functional imaging techniques such as positron emission tomography, electroencephalography, magnetoencephalography, and electrocardiography.
Psychopathology is the study of mental illness, particularly of severe disorders. Informed heavily by both psychology and neurology, its purpose is to classify mental illness, elucidate its underlying causes, and guide clinical psychiatric treatment accordingly. Although diagnosis and classification of mental norms and disorders is largely the purview of psychiatry and other social sciences, the results of which are guidelines such as the Diagnostic and Statistical Manual of Mental Disorders, the field is also heavily, and increasingly, informed upon by neuroscience and other of the biological cognitive sciences. Mental or social disorders or behaviours which are seen to be generally unhealthy or excessive in a given individual to the point where they cause harm or severe disruption to the sufferer's lifestyle are often given the the handle of "pathological" (e.g. pathological gambling).
The Study of pathology in non-humans
Although the vast majority of lab work and research in pathology concerns the development of disease in humans, pathology is of significance throughout the biological sciences. Two main catch-all fields exist to represent most complex organisms capable of serving as host to a pathogen or other form of disease: veterinary pathology (concerned with all non-human species of kingdom of Animalia, and phytopathology, which studies disease in plants.
Veterinary pathology covers a vast array of species, but with a significantly smaller number of practitioners, so understanding of disease in non-human animals, especially as regards veterinary practice, varies considerably by species. Nonetheless, significant amounts of pathology research are conducted on animals (see Animal testing), for two primary reasons: 1) The origins of diseases are typically zoonotic in nature, and many infectious pathogens have animal vectors and so understanding the mechanisms of action for these pathogens in non-human hosts is essential to the understanding and application of epidemiology and 2) those animals which share physiological and genetic traits with humans can be used as surrogates for the study of the disease and it's potential treatments as well as the effects of various synthetic products. For this reason, as well as their roles as livestock and companion animals, mammals generally have the largest body of research in veterinary pathology. Animal testing remains a controversial practice, even in cases where it is used to research treatment for human disease. In regular veterinary practice, pathology mimics the major division of testing into anatomical and clinical pathology.
Although the pathogens and their mechanics differ greatly from those of animals, plants are subject to a wide variety of diseases, including those caused by fungi, oomycetes, bacteria, viruses, viroids, virus-like organisms, phytoplasmas, protozoa, nematodes and other (parasitic) plants. Damage caused by insects, mites, vertebrate, and other small herbivores is not considered a part of the domain of plant pathology. The field is deeply connected to plant disease epidemiology and the horticulture of species which are of high importance to human diet or other uses.
- Causal inference
- Cell (biology)
- Diagnostic medicine
- Etiology (medicine)
- List of pathologists
- Medical science
- Precision medicine
- Speech-Language Pathology
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- Homepage of the American Board of Pathology
- Reglementation for French Residency in Clinical Pathology (Biologie médicale)
- curriculum content of French resident training in clinical pathology, First Level and Second Level
- American Society for Investigative Pathology (ASIP)
- Pathpedia online pathology resource: Comprehensive pathology website with numerous resources.
- College of American Pathologists
- humpath.com (Atlas in Human Pathology)
- Intersociety Council for Pathology Training (ICPI)
- Pathological Society of Great Britain and Ireland
- Royal College of Pathologists (UK)
- Royal College of Pathologists of Australasia (Australia & Oceania)
- United States and Canadian Academy of Pathology
- WebPath: The Internet Pathology Laboratory for Medical Education
- Atlases: High Resolution Pathology Images
- pathologybook.info the most comprehensive book information of pathology-related
- pushglass: pathology image search