Pathology

Pathology (from Greek pathos, feeling, pain, suffering; and logos, study of; see also -ology) is the study of the processes underlying disease and other forms of illness, harmful abnormality, or dysfunction. Within biology but also a branch of medicine, it means specifically the study and diagnosis of the structural and functional changes in molecules, cells, tissues and organs that underlie disease. Pathology as a field of knowledge hence forms the basis of the scientific reasoning behind the practice of medicine.

Scope of pathology
The primary goal of pathology is the study of the four main aspects of a disease:
 * Etiology: what causes the disease
 * Pathogenesis: the mechanism by which a certain etiological factor causes disease
 * Morphologic changes: the structural changes induced in the cells, tissues and organs
 * Clinical significance: the functional consequences of the morphologic changes

Pathologists' work
Because the public rarely meets pathologists, their work is not well understood. Pathology is a large and diverse field that allows a pathologist to participate in multiple areas of the field or focus their scope to a specific area. Essential to everyday surgeries, pathologists are responsible for processing and reporting on all specimens generated during surgery. Tissue samples are taken from the submitted specimens, stained, and processed for microscopic evaluation. Microscopic examination searches for disease of any type and this information is returned to the surgeon via a pathology report. They, along with Pathologists' Assistants and Medical Technologists, process specimens at medical laboratories for interpretations. In other words, when a doctor refers to a "laboratory result", they are not referring to a number generated by a black box; instead, it is the interpretation of a value by a pathologist or a technologist. It is also important to understand that a different laboratory might produce a different value on the same specimen. Pathologists are also called upon to perform autopsies; they are usually assisted by Dieners. Autopsies represent less than 5% of the workload of a typical modern pathologist. There exists a subspecialty in pathology that allows for the training of medical examiners who wish to pursue forensics.

Pathologists usually do not see patients, but do on occasion such as when performing bone marrow biopsies and aspirates or fine needle aspirations of superficial nodules. Thus, it is best considered a form of diagnostic medicine. In addition to the diagnosis of disease, including cancer, and the administration of medical laboratories, pathologists often participate in the teaching of medical students (pathology is a core course in the medical curriculum). Pathologists express their opinion as a pathology report addressed to the doctor requesting it. Since pathologists most often communicate with other doctors, they are sometimes nicknamed "the doctor's doctor." Pathology is often considered the most scientific branch of medicine because of the available avenues of research involving human material. Finally, the circulation of laboratory data is a central issue in medical informatics and the current tendency towards electronic medical records.

Tools of pathology
The techniques used most often in the study of the disease process and hence diagnosis are:
 * Gross pathology: the recognition of disease based on macroscopic examination of surgical specimens generated at the time of surgery or at autopsy.
 * Histology: the microscopic study of tissues. Histopathology is the science of diagnosing diseases on the basis of the histological aspect of the diseased tissues.
 * Cytology: the study of detached cells. Cytopathology is the science of diagnosing diseases on the basis of the cytological aspects of detached cells. The most common application of this technique is the Pap smear.
 * Clinical chemistry: the gathering, detection, and reporting of an incredible array of chemical measures found by the analysis of collected body samples.
 * Immunology: the use of specific immune markers and antibodies to aid in the diagnosis of disease.
 * Flow cytometry: analysis of a process that allows for the identification of specific cells.
 * Molecular Biology techniques, like PCR and FISH are increasingly useful to diagnose diseases, especially microbiological and cancer diagnoses.

Medicine
In the United States, pathologists are medical doctors (MD) or doctors of osteopathic medicine (DO), that have completed a four year undergraduate program, four years of medical school training, and four to five 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: Most pathologists seek a broad based training in both fields and thus require four years of postgraduate training known as residency. Board certification examination is required. Boarding requirements are set by the American Board of Pathology. Following the general training, many pathologists continue on to more specialized training within specific fields of pathology. This speciality training is termed a fellowship. Multiple fellowship opportunities are available within both Anatomical and Clinical Pathology. Examples of fellowhips include General Surgical Pathology, Gastrointestinal Pathology, Genitourinary pathology, Hematopathology, Dermatopathology, Microbiology, and Clinical Chemistry. These are but a few of the numerous fields within pathology. Some of the speciality areas of pathology are board certified while others are not. Pathologists, like all other medical doctors, require a medical license from the State they are working in to practice their field. This entails meeting continuing medical education requirements to maintain licensure.
 * Anatomic Pathology, the science of diagnosing diseases based on the appearance of tissues, both gross and microscopic.
 * Clinical Pathology, the science of diagnosing diseases based on the analysis of body fluids like blood, urine, etc.

Dentistry
The American Board of Oral and maxillofacial pathology certifies dentistry doctors, not medical doctors, to practice this sub-specialty of pathology.

Experimental pathology
Experimental pathology (or investigative pathology), is the study of disease mechanisms and pathophysiology.

Most of the work of investigative pathologists is carried out in the laboratory. Tissue culture, polymerase chain reaction (PCR), ELISA, western blot, southern blot, northern blot and many other biotechnological methods are required to identify differences between normal and disease states in different cell types with regards to DNA, RNA, and protein as well as determining the influence of these differences on the organism as a whole.

Other

 * Plant pathology
 * Veterinary pathology
 * Parasitology


 * Speech pathology is an unrelated area mostly involved in helping patients with stroke or speech impediments.
 * Psychopathology is also used in mental health, denoting the study of mental illness.

Related sciences

 * Anatomy, either gross or microscopic (histology)
 * Nosology: the science of classifying, or naming, diseases
 * Epidemiology: the science of associating diseases with risk factors, regardless of known pathological relationships. An epidemiological association is often the first step in establishing an etiological (causal) relationship between a risk factor and a disease.

Other uses of "pathology"
Pathological is used to describe a person's actions in such a way as to credit the action to a disease process, e.g. pathological purchasing or pathological consumption, pathological narcissism, pathological liar, pathological gambling, pathological jealousy. Pathological is also used casually, to signify an abnormal state, e.g. a "pathological attitude" or a "pathological woman hater".

Pathological is also used in mathematics, physics, and statistics to describe an exceptionally (or awkwardly, or inconveniently) atypical example or set of data, often one which does not abide by rules or succumb to treatment that other similar cases usually do:
 * Pathological (mathematics)
 * Pathological science

Computer science uses this term in a slightly different sense with regard to the study of algorithms. Here, an input (or set of inputs) is said to be pathological if it causes atypical behavior from the algorithm, such as a violation of its average case complexity, or even its correctness. For example, hash tables generally have pathological inputs: sets of keys that collide on hash values. The term is often used pejoratively, as a way of dismissing such inputs as being specially designed to break a routine that is otherwise sound in practice.

Forensic Engineers often use the term to describe the underlying causes of distress in structures or machinery in order to specify repairs.