Pathology

Pathology is the precise 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, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling. Pathologies (or pathoses) is synonymous with diseases. The suffix "path" is used to indicate a state of disease, and may be used to indicate psychological (e.g. psychopath) or physical disease (e.g. cardiomyopathy). 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).

Pathology is further separated into divisions, based on either the system being studied (e.g. dermatopathology) or the focus of the examination (e.g. forensic pathology and determining the cause of death).

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 (autopsy).

Anatomical pathology is itself divided in subspecialties, the main ones being surgical pathology, cytopathology, and forensic pathology. To be licensed to practice pathology, one has to complete medical school and secure a license to practice medicine. An approved residency program and certification (in the United States, the American Board of Pathology or the American Osteopathic Board of Pathology) is usually required to obtain employment or hospital privileges.

Anatomical pathology is one of two branches of pathology, the other being clinical pathology, the diagnosis of disease through the laboratory analysis of bodily fluids and tissues. Often, pathologists practice both anatomical and clinical pathology, a combination known as general pathology. The distinction between anatomic and clinical pathology is increasingly blurred by the introduction of technologies that require new expertise and the need to provide patients and referring physicians with integrated diagnostic reports. Similar specialties exist in veterinary pathology.

Clinical pathology
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, and tissues using the tools of chemistry, microbiology, hematology and molecular pathology. Clinical pathologists work in close collaboration with medical technologists, hospital administrations, and referring physicians to ensure the accuracy and optimal utilization of laboratory testing.

Clinical pathology is one of the two major divisions of pathology, the other being anatomical pathology. Often, pathologists practice both anatomical and clinical pathology, a combination sometimes known as general pathology.

Dermatopathology
Dermatopathology is a subspecialty of anatomic pathology that focuses on the skin as an organ. It is unique in that there are two routes which a physician can use to obtain this specialization. All general pathologists and general dermatologists are trained in the pathology of the skin; however, the dermatopathologist is a specialist in this organ. 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.

Hematopathology
Hematopathology is the study of diseases of blood cells (White blood cells, red blood cells, platelets) and cells/tissues/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, lymph node, 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. After the hematopathologist makes the diagnosis, the hematologist or hemato-oncologist can make a decision about the best course of action.

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.

Forensic pathology
Forensic pathology is a branch of pathology concerned with determining the cause of death by examination of a cadaver. The autopsy is performed by the pathologist at the request of a coroner usually during the investigation of criminal law cases and civil law cases in some jurisdictions. Forensic pathologists are also frequently asked to confirm the identity of a cadaver.

The word forensics is derived from the Latin forēnsis meaning forum.

Molecular pathology
Molecular pathology is an emerging discipline within pathology, and focuses in the study and diagnosis of disease through the examination of molecules within organs, tissues or bodily fluids. Molecular pathology shares some aspects of practice with both anatomic pathology and clinical pathology, molecular biology, biochemistry, proteomics and genetics, and is sometimes considered a "crossover" discipline. It is multi-disciplinary in nature and focuses mainly on the sub-microscopic aspects of disease and unknown illnesses with strange causes.

It is a scientific discipline that encompasses the development of molecular and genetic approaches to the diagnosis and classification of human tumors, the design and validation of predictive biomarkers for treatment response and disease progression, the susceptibility of individuals of different genetic constitution to develop cancer, and the environmental and lifestyle factors implicated in carcinogenesis.

Molecular pathological epidemiology
Integration of "molecular pathology" and "epidemiology" led to an interdisciplinary field, termed "molecular pathological epidemiology (MPE)", which represents integrative molecular biologic and population health science. MPE is a specific discipline of epidemiology, and also that of pathology, representing an interface between pathology and public health. Pathology and epidemiology have a common goal of elucidating etiology of disease, and integrative MPE aims to achieve this goal simultaneously at molecular, individual, and population levels. Essentially, each individual has a unique disease process different from any other individual (“the unique disease principle”), considering uniqueness of the exposome and its unique influence on molecular pathologic processes (including alterations in the interactome) in each individual. This principle was first described in neoplastic diseases as "the unique tumor principle". The MPE approach can be applied to not only neoplastic diseases but also non-neoplastic diseases. The MPE paradigm has been globally adopted and in widespread use. In MPE, investigators analyze relationships between (A) exposures; (B) alterations in cellular or extracellular molecules (disease molecular signatures); and (C) evolution and progression of disease. As disease molecular signatures, investigators can analyze genome, methylome, epigenome, metabolome, transcriptome, proteome, microbiome, and interactome. The MPE research enables identification of a new biomarker for potential clinical utility, using a large-scale population based data (e.g., PIK3CA mutation in colorectal cancer to select patients for aspirin therapy ). The MPE approach can be used as one of next steps from genome-wide association study (GWAS) (“GWAS-MPE Approach”). Detailed disease endpoint phenotyping can be conducted by means of molecular pathology or surrogate histopathology or immunohistochemistry analysis of diseased tissues and cells within GWAS. As an alternative approach, potential risk variants identified by GWAS can be examined in combination with molecular pathology analysis on diseased tissues. This GWAS-MPE approach can give not only more precise effect estimates, even larger effects, for specific molecular subtypes of the disease, but also insights into pathogenesis by linking genetic variants to molecular pathologic signatures of disease. A better understanding of heterogeneity of disease pathogenesis can help to elucidate etiologies and causations of diseases. In particular, with the emergence of MPE, a possible risk factor can now be linked to specific molecular signatures of a disease. Thus, MPE can advance the area of causal inference.

Because heterogeneity of disease etiologies and pathogenesis is a ubiquitous phenomenon, the MPE paradigm will become inherent in epidemiology and population health sciences. Since molecular diagnostics is becoming routine clinical practice in the era of precision medicine, molecular pathology data will accumulate in human populations and can be utilized in a wide spectrum of epidemiology research.

France
In France, Pathology is separate in two distinct specialties, Anatomical pathology and Clinical pathology. Residencies 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 practise Anatomical pathology. And conversely, Anatomical pathology residents can not practise Clinical pathology.

United Kingdom
In the United Kingdom, pathologists are medical doctors registered with — and currently 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 programme. Full-time training in Histopathology currently lasts between five and five and a half years. The first year involves structured training and is assessed by an objective structured practical exam (OSPE), which must be passed to progress to year two. This is followed by further specialist training in surgical pathology, cytopathology, and autopsy 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 four or five years of specialist training. All postgraduate medical training and education in the UK is overseen by the General Medical Council (GMC). It is possible to take a specialist part 2 examination in forensic pathology, pediatric pathology, or neuropathology. It is also possible to take a Royal College of Pathologists diploma in forensic pathology, dermatopathology, or cytopathology, recognising additional specialist training and expertise.

United States
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. Many pathologists pursue 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 intermittently requires the attention of a physician. Thus, pathologists are able to spend much of their time evaluating anatomical 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 subspecialties of either anatomical or clinical pathology. Some of these subspecialties permit additional board certification, while others do not.

History
The history of pathology can be traced back to antiquity when people began examining bodies. The examination of bodies led to the dissection of bodies in order to discover the cause of death. During that time, the people already began formulating today what we know as inflammation, tumors, boils, and much more.

Pathology began to develop as a subject during the 19th Century through teachers and physicians that studied pathology. They referred to it as “pathological anatomy” or “morbid anatomy.” However, pathology as a field of medicine was not recognized until the late 19th and early 20th centuries. In the 19th century, physicians realized that disease-causing pathogens, or germs (disease-causing, or pathogenic, microbes, such as bacteria, viruses, fungi, amoebae, molds, protists, and prions) existed and were capable of reproduction and multiplication, and that evil spirits or humors, or even the signs and symptoms of the condition, were not the causative agent of a disease. Through the new information gathered regarding germ reproduction, 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 create themselves, and that they can affect human beings in unique ways. In order to determine causes of diseases, medical experts used the most common and widely accepted assumptions or symptoms of their times. This is true for those in the past and today.

What set pathology apart from other specialties was the ability to determine a symptom with the naked eye. During the 19th century, Rudolf Virchow gave the biggest contribution to the field by introducing the procedure of analyzing tissue and cells through a microscope to pathologists. This greatly affected the discipline because it was another way to analyze objects, and it led to more advanced technological developments.

By the late 1920s to early 1930s pathology was deemed a medical specialty. During the years following, the decision to split pathology into sub-specialties arose. Today, anatomical, clinical, molecular, forensic, oral, dermatopathology, hematopathology, and neuropathology exist as medical specialties. Today, pathologists are physicians who are diagnosing patients with diseases through examination of biopsies and resections. Their work also includes working with other physicians and scientists on solutions to treat diseases such as various kinds of cancers.