pathology pathology pathology is the study of the causes and effects of disease or injury. the word pathology also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. however, when used in the context of modern medical treatment, the term is often used in a narrower fashion to refer to processes and tests that fall within the contemporary medical field of "general pathology", an area which includes a number of distinct but inter-related medical specialties that diagnose disease, mostly through analysis of tissue and human cell samples. idiomatically, "a pathology" may also refer to the predicted or actual progression of particular diseases (as in the statement "the many different forms of cancer have diverse pathologies", in which case a more proper choice of word would be "pathophysiologies"), and the affix pathy is sometimes used to indicate a state of disease in cases of both physical ailment (as in cardiomyopathy) and psychological conditions (such as psychopathy). a physician practicing pathology is called a pathologist. pathologya pathologist examines a tissue section for evidence of cancerous cells while a surgeon observes.focusdiseasesubdivisionsanatomical pathology, clinical pathology, dermatopathology, forensic pathology, hematopathology, histopathology, molecular pathology, surgical pathologysignificant diseasesall infectious and organic diseases and physiological disorderssignificant testsall medical diagnostic tests, particular biopsy, blood analysis, dissection, and other applications of medical microscopyspecialistpathologistglossaryglossary of medicine pathologistoccupationnames physician surgeon occupation typespecialtyactivity sectorsmedicine, surgerydescriptioneducation required doctor of medicine (m.d.) doctor of osteopathic medicine (d.o.) doctor of veterinary medicine (d.v.m) bachelor of medicine, bachelor of surgery (m.b.b.s./m.b.ch.b.) fields ofemploymenthospitals, clinics as a field of general inquiry and research, pathology addresses components of disease: cause, mechanisms of development (pathogenesis), structural alterations of cells (morphologic changes), and the consequences of changes (clinical manifestations). in common medical practice, general pathology is mostly concerned with analyzing known clinical abnormalities that are markers or precursors for both infectious and non-infectious disease, and is conducted by experts in one of two major specialties, anatomical pathology and clinical pathology. further divisions in specialty exist on the basis of the involved sample types (comparing, for example, cytopathology, hematopathology, and histopathology), organs (as in renal pathology), and physiological systems (oral pathology), as well as on the basis of the focus of the examination (as with forensic pathology). pathology is a significant field in modern medical diagnosis and medical research. history main article: history of medicine the advent of the microscope was one of the major developments in the history of pathology. here researchers at the centers for disease control in 1978 examine cultures containing legionella pneumophila, the pathogen responsible for legionnaire's disease. 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 hippocrates, for whom the modern hippocratic 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, growth in complex understanding of disease mostly languished until knowledge and experimentation again began to proliferate in the renaissance, enlightenment, and baroque eras, following the resurgence of the empirical method at new centers of scholarship. by the 17th century, the study of rudimentary microscopy 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 approach 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. 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 distinct fields, resulting in the development of a large number of modern specialties within pathology and related disciplines of diagnostic medicine. etymology the term pathology comes from the ancient greek roots of pathos (πάθος), meaning "experience" or "suffering" and -logia (-λογία), "study of". the latin term is of early sixteenth-century origin and became increasingly popularized after the 1530s. general pathology a modern pathology lab at the services institute of medical sciences the modern practice of pathology is divided into a number of subdisciplines within the distinct but deeply interconnected aims of biological research and medical practice. biomedical research into disease incorporates the work of a vast variety of life science specialists, whereas, in most parts of the world, to be licensed to practice pathology as a 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 that study or diagnose markers for disease using methods and technologies particular to specific scales, organs, and tissue types. the information in this section mostly concerns pathology as it regards common medical practice in these systems, but each of these specialties is also the subject of voluminous pathology research as regards the disease pathways of specific pathogens and disorders that affect the tissues of these discrete organs or structures. anatomical pathology main article: anatomical pathology 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 divisions 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 main article: cytopathology a bone marrow smear from a case of erythroleukemia. the large cell in the top center is an abnormal erythroblast: it is multinucleated, with megaloblastoid nuclear chromatin this is diagnostic of erythroleukemia. 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. dermatopathology main article: dermatopathology a malignant melanoma can often be suspected from sight, but confirmation of the diagnosis or outright removal requires an excisional biopsy. 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 paths a physician can take to obtain the specialization. all general pathologists and general dermatologists train in the pathology of the skin, so the term dermatopathologist denotes either of these who has reached a certainly level of accreditation and experience; in the us, 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 lead to a conclusive diagnosis, 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. forensic pathology main article: forensic pathology pathologist performing a human dissection of the abdominal and thoracic organs in an autopsy room forensic pathology focuses on determining the cause of death by post-mortem examination of a corpse or partial remains. an autopsy is typically performed by a coroner or medical examiner, often during criminal 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 (and even within a given nation) but typically a minimal requirement is a medical doctorate with a specialty in general or anatomical pathology with subsequent study in forensic medicine. the methods forensic scientists use to determine death include examination of tissue specimens to identify the presence or absence of natural disease and other microscopic findings, interpretations of toxicology on body tissues and fluids to determine the chemical cause of overdoses, poisonings or other cases involving toxic agents, and examinations of physical trauma. forensic pathology is a major component in the trans-disciplinary field of forensic science. histopathology main article: histopathology an instance of diagnosis via histopathology, this high-magnification micrograph of a section of cardiac tissue reveals advanced cardiac amyloidosis. this sample was attained through an autopsy. 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 uses 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 that 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