Histology, also known as microscopic anatomy or microanatomy, is the branch of biology that studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures visible without a microscope. Although one may divide microscopic anatomy into organology, the study of organs, histology, the study of tissues, and cytology, the study of cells, modern usage places all of these topics under the field of histology. In medicine, histopathology is the branch of histology that includes the microscopic identification and study of diseased tissue. In the field of paleontology, the term paleohistology refers to the histology of fossil organisms.
Haematoxylin or hematoxylin, also called natural black 1 or C.I. 75290, is a compound extracted from heartwood of the logwood tree with a chemical formula of C
16H
14O
6. This naturally derived dye has been used as a histologic stain, ink and as a dye in the textile and leather industry. As a dye, haematoxylin has been called Palo de Campeche, logwood extract, bluewood and blackwood. In histology, haematoxylin staining is commonly followed (counterstained), with eosin, when paired, this staining procedure is known as H&E staining, and is one of the most commonly used combinations in histology. In addition to its use in the H&E stain, haematoxylin is also a component of the Papanicolaou stain which is widely used in the study of cytology specimens.
Eosin is the name of several fluorescent acidic compounds which bind to and form salts with basic, or eosinophilic, compounds like proteins containing amino acid residues such as arginine and lysine, and stains them dark red or pink as a result of the actions of bromine on eosin. In addition to staining proteins in the cytoplasm, it can be used to stain collagen and muscle fibers for examination under the microscope. Structures that stain readily with eosin are termed eosinophilic. In the field of histology, Eosin Y is the form of eosin used most often as a histologic stain.
Staining is a technique used to enhance contrast in samples, generally at the microscopic level. Stains and dyes are frequently used in histology, in cytology, and in the medical fields of histopathology, hematology, and cytopathology that focus on the study and diagnoses of diseases at the microscopic level. Stains may be used to define biological tissues, cell populations, or organelles within individual cells.
Histopathology refers to the microscopic examination of tissue in order to study the manifestations of disease. 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. In contrast, cytopathology examines free cells or tissue micro-fragments.
Basophilic is a technical term used by pathologists. It describes the appearance of cells, tissues and cellular structures as seen through the microscope after a histological section has been stained with a basic dye. The most common such dye is haematoxylin.
Fibrinoid necrosis is a specific pattern of irreversible, uncontrolled cell death that occurs when antigen-antibody complexes are deposited in the walls of blood vessels along with fibrin. It is common in the immune-mediated vasculitides which are a result of type III hypersensitivity. When stained with hematoxylin and eosin, they appear brightly eosinophilic and smudged.
Fibroadenomas are benign breast tumours characterized by an admixture of stromal and epithelial tissue. Breasts are made of lobules and ducts. These are surrounded by glandular, fibrous and fatty tissues. Fibroadenomas develop from the lobules. The glandular tissue and ducts grow over the lobule to form a solid lump.
Eosin Y, also called C.I. 45380 or C.I. Acid Red 87, is a member of the triarylmethane dyes. It is produced from fluorescein by bromination.
Masson's trichrome is a three-colour staining procedure used in histology. The recipes evolved from Claude L. Pierre Masson's (1880–1959) original formulation have different specific applications, but all are suited for distinguishing cells from surrounding connective tissue.
Papanicolaou stain is a multichromatic (multicolored) cytological staining technique developed by George Papanicolaou in 1942. The Papanicolaou stain is one of the most widely used stains in cytology, where it is used to aid pathologists in making a diagnosis. Although most notable for its use in the detection of cervical cancer in the Pap test or Pap smear, it is also used to stain non-gynecological specimen preparations from a variety of bodily secretions and from small needle biopsies of organs and tissues. Papanicolaou published three formulations of this stain in 1942, 1954, and 1960.
Hematoxylin and eosin stain is one of the principal tissue stains used in histology. It is the most widely used stain in medical diagnosis and is often the gold standard. For example, when a pathologist looks at a biopsy of a suspected cancer, the histological section is likely to be stained with H&E.
Cytoarchitecture, also known as cytoarchitectonics, is the study of the cellular composition of the central nervous system's tissues under the microscope. Cytoarchitectonics is one of the ways to parse the brain, by obtaining sections of the brain using a microtome and staining them with chemical agents which reveal where different neurons are located.
A koilocyte is a squamous epithelial cell that has undergone a number of structural changes, which occur as a result of infection of the cell by human papillomavirus (HPV). Identification of these cells by pathologists can be useful in diagnosing various HPV-associated lesions.
Acidophile is a term used by histologists to describe a particular staining pattern of cells and tissues when using haematoxylin and eosin stains. Specifically, the name refers to structures which "love" acid, and take it up readily. More specifically, acidophilia can be described by cationic groups of most often proteins in the cell readily reacting with acidic stains.
Usual interstitial pneumonia (UIP) is a form of lung disease characterized by progressive scarring of both lungs. The scarring (fibrosis) involves the pulmonary interstitium. UIP is thus classified as a form of interstitial lung disease.
Toluidine blue, also known as TBO or tolonium chloride (INN) is a blue cationic (basic) dye used in histology and sometimes clinically.
Infantile digital fibromatosis (IDF), also termed inclusion body fibromatosis, Reye tumor, or Reye's tumor, usually occurs as a single, small, asymptomatic, nodule in the dermis on a finger or toe of infants and young children. IMF is a rare disorder with approximately 200 cases reported in the medical literature as of 2021. The World Health Organization, 2020, classified these nodules as a specific benign tumor type in the category of fibroblastic and myofibroblastic tumors. IDF was first described by the Australian pathologist, Douglas Reye, in 1965.
Luxol fast blue stain, abbreviated LFB stain or simply LFB, is a commonly used stain to observe myelin under light microscopy, created by Heinrich Klüver and Elizabeth Barrera in 1953. LFB is commonly used to detect demyelination in the central nervous system (CNS), but cannot discern myelination in the peripheral nervous system.
A "red neuron" is a pathological finding in neurons, generally of the central nervous system, indicative of acute neuronal injury and subsequent apoptosis or necrosis. Acidophilic neurons are often found in the first 12–24 hours after an ischemic injury such as a stroke. Since neurons are permanent cells, they are most susceptible to hypoxic injury. The red coloration is due to pyknosis or degradation of the nucleus and loss of Nissl bodies which are normally stained blue (basophilic) on hematoxylin & eosin staining. This leaves only the degraded proteins which stains red (eosinophilic). Acidophilic neurons also can be stained with acidic dyes other than eosin.
