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.
    * 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 immunhistochemistry, 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.