Anatomical pathology

Anatomical pathology (Commonwealth) or Anatomic pathology (U.S.) is a medical specialty that is concerned with the diagnosis of disease based on the gross, microscopic, and molecular examination of organs, tissues, and cells. In many countries, physicians who practice pathology are trained in both anatomical pathology and clinical pathology, the diagnosis of disease through the laboratory analysis of bodily fluids.

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.

Skills and procedures
The procedures used in anatomic pathology include:


 * Gross examination - the examination of diseased tissues with the naked eye. This is important especially for large tissue fragments, because the disease can often be visually identified. It is also at this step that the pathologist selects areas that will be processed for histopathology. The eye can sometimes be aided with a magnifying glass or a stereo microscope, especially when examining parasitic organisms.
 * Histopathology - the microscopic examination of stained tissue sections using histological techniques. The standard stains are haematoxylin and eosin, but many others exist. The use of haematoxylin and eosin-stained slides to provide specific diagnoses based on morphology is considered to be the core skill of anatomic pathology. The science of staining tissues sections is called histochemistry.
 * Immunohistochemistry - the use of antibodies to detect the presence, abundance, and localization of specific proteins. This technique is critical to distinguishing between disorders with similar morphology, as well as characterizing the molecular properties of certain cancers.
 * In situ hybridization - Specific DNA and RNA molecules can be identified on sections using this technique. When the probe is labeled with fluorescent dye, the technique is called FISH.
 * Cytopathology - the examination of loose cells spread and stained on glass slides using cytology techniques.
 * Electron microscopy - the examination of tissue with an electron microscope, which allows much greater magnification, enabling the visualization of organelles within the cells. Its use has been largely supplanted by immunohistochemistry, but it is still in common use for certain tasks, including the diagnosis of kidney disease and the identification of immotile cilia syndrome among many others.
 * Tissue cytogenetics - the visualization of chromosomes to identify genetics defects such as chromosomal translocation.
 * Flow immunophenotyping - the determination of the immunophenotype of cells using flow cytometry techniques. It is very useful to diagnose the different types of leukemia and lymphoma.

Surgical pathology
Surgical pathology is the most significant and time-consuming area of practice for most anatomical pathologists. Surgical pathology involves the gross and microscopic examination of surgical specimens, as well as biopsies submitted by non-surgeons such as general internists, medical subspecialists, dermatologists, and interventional radiologists.

Cytopathology
Cytopathology is a sub-discipline of anatomical pathology concerned with the microscopic examination of whole, individual cells obtained from smears or fine needle aspirates. Cytopathologists are trained to perform fine-needle aspirates of superficially located organs, masses, or cysts, and are often able to render an immediate diagnosis in the presence of the patient and consulting physician. In the case of screening tests such as the Papanicolaou smear, non-physician cytotechnologists are often employed to perform initial reviews, with only positive or uncertain cases examined by the pathologist. Cytopathology is a board-certifiable subspecialty in the U.S.

Molecular Pathology
Molecular pathology is an emerging discipline within anatomical pathology which is focused on the use of nucleic acid-based techniques such as in-situ hybridization, reverse-transcriptase polymerase chain reaction, and nucleic acid microarrays for specialized studies of disease in tissues and cells. Molecular pathology shares some aspects of practice with both anatomic and clinical pathology, and is sometimes considered a "crossover" discipline.

Autopsy pathology
General anatomical pathologists are trained in performing autopsies, which are used to determine the disease factors contributing to a person's death. Autopsies are important in the ongoing medical education of clinicians, and in efforts to improve and verify the quality of medical care. Dieners are non-physicians who assist pathologists in the gross dissection portion of the autopsy. Autopsies represent less than 10% of the workload of typical pathologists in the United States. However, the autopsy is central to public perceptions of the field, in part due to portrayals of pathologists on television programs such as Quincy, M.E. and Silent Witness.

Forensic pathology
Forensic pathologists receive specialized training in determining the cause of death and other legally relevant information from the bodies of persons who died in a non-medical or potentially criminal circumstances. Autopsies make up much, but not all of the work of the practicing forensic pathologist, and forensic pathologists are occasionally consulted to examine a survivor of a criminal attack. Forensic pathology is a board-certifiable sub-specialty in the U.S.

USA
Anatomic Pathology (AP) is one of the two primary certifications offered by the American Board of Pathology. The other is Clinical Pathology (CP). To be certified in anatomic pathology, the trainee must complete four years of medical school followed by three years of residency training. Many US pathologists are certified in both AP and CP, which requires a total of four years of residency. After completing residency, many pathologists enroll in further years of fellowship training to gain expertise in a subspecialty of AP.

Canada
Anatomical Pathology (AP) is one of the specialist certificates granted by the Royal College of Physicians and Surgeons of Canada. Other certificates related to pathology include general pathology (GP), forensic pathology, hematopathology, and neuropathology. Candidates for any of these must have completed four years of medical school and five years of residency training. After becoming certified in either AP or GP, it is common for pathologists to seek further fellowship training in a subspecialty of AP.

Anatomical pathology practice settings

 * Academic anatomical pathology is practiced by pathologists who are also faculty members of a university medical center often have a diverse set of responsibilities, such are practicing diagnostic anatomical pathology, conducting basic or translational research, training pathology residents, and teaching medical students. Anatomical pathologists in the academic setting are often more specialized in a specific area of expertise, than their private-practice counterparts.


 * Group practice is the most traditional private practice model. In this arrangement, a group of senior pathologists will control a partnership which employs more junior pathologists, and which contracts independently with hospitals to provide diagnostic services, as well as attracting referral business from local clinicians who practice in the outpatient setting. The group often owns a lab for histology and ancillary testing of tissue, and may hold contracts to run hospital-owned labs. Many pathologists who practice in this setting are trained and certified in both anatomical pathology and clinical pathology, which allows them to blood banks, clinical chemistry laboratories, and medical microbiology laboratories as well.


 * Large corporate providers of anatomical pathology services have emerged in recent years, most notably AmeriPath in the United States. In this model, pathologists are employees, rather than independent partners. This model has been criticized for reducing physician independence, but defenders claim that the larger size of these practices allow for economies of scale and greater specialization, as well a sufficient volume to support more specialized testing methods.


 * Multispecialty groups, composed of physicians from clinical specialties as well as radiology and pathology, are another practice model. In some case, these may be large groups controlled by an HMO or other large health care organization. In others, they are essentially clinician group practices which employ pathologists to provide diagnostic services for the group. These groups may own their own laboratories, or, in some cases have made controversial arrangements with "pod labs" which allow clinician groups to lease space, with the clinican groups receiving direct insurance payments for pathology services. Proposed changes to Medicare regulations may essentially eliminate these arrangements in the United States.