Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

154 results found
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McMurray test

The McMurray test is used to assess the presence of meniscal tears within the knee. Background Clinical tests used for the detection of meniscal tears provide varying levels of diagnostic parameters including sensitivity and specificity. MRI is considered the most accurate diagnostic tool for ...
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Metaplasia

Metaplasia is a general pathology term that refers to process when one cell type is replaced by another. It usually occurs in the context of a changed cellular environment to which the new cell type is better adapted 1. Examples include 2-5: Barrett esophagus: normal squamous epithelium replace...
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Microglia

Microglia is one of the four types of glial cell and are the central nervous system equivalent of monocyte-macrophage system 1,2. During health, they are essentially inactive with small cell bodies and numerous processes extending throughout the local parenchyma 1,2. When presented a condition w...
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Micrometastasis

Micrometastases are defined by the UICC TNM Classification of Malignant Tumors as conglomerations of tumor cells measuring between 0.2 mm and 2 mm in size. Clusters of cells sized less than 0.2 mm in maximal dimension are termed isolated tumor cells (ITCs). Tumor clusters measuring larger than 2...
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Molybdenum

Molybdenum (chemical symbol Mo) is one of the essential trace elements. It complexes with a molecule called molybdopterin to form molybdenum cofactor, essential for the functioning of several important metabolic enzymes.  Chemistry Basic chemistry Molybdenum has the atomic number 42, with an ...
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Multilocular cystic renal neoplasm of low malignant potential

Multilocular cystic renal neoplasm of low malignant potential  is a low-grade adult renal tumor composed entirely of numerous cysts. The entity was previously known as multilocular cystic renal cell carcinoma, which usually had clear cell morphology, but was redefined in the 2016 WHO classificat...
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Mycobacterium tuberculosis

Mycobacterium tuberculosis is a thin, slightly curved bacillus. A member of the Mycobacterium tuberculosis complex, it is an obligate aerobic bacterium that is the etiologic agent of the majority of tuberculosis cases.  Epidemiology The worldwide incidence of tuberculosis was 8.7 million in 20...
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Myoinositol peak

Myoinositol is one of the compounds images with MR spectroscopy (MRS) at both 1.5 T and 3 T and is seen to resonate at 3.5 ppm chemical shift (right of the choline peak).  Myoinositol is a precursor of both phosphatidylinositol (the major inositol-containing phospholipid) and of phosphatidylino...
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Neuritic plaques

Neuritic plaques (also known as senile plaques) are pathological extracellular aggregates formed around a core of amyloid β peptide and are a hallmark of Alzheimer's disease.  They should not be confused with neurofibrillary tangles which are intracytoplasmic. Pathology Neuritic plaques are e...
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Neurofibrillary tangles

Neurofibrillary tangles (NFTs) are abnormal cytoplasmic accumulations of tau proteins, found in neuronal and glial cells of the central nervous system. They are responsible for a number of neurodegenerative diseases (collectively known as tauopathies) including 1: progressive supranuclear palsy...
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Neurofibromin

Neurofibromin is a protein coded for by the NF1 gene located on chromosome 17 (17q11.2). It is a multifunctional protein and is involved in the regulation of many cellular signaling pathways. In patients with a mutation of the NF1 gene, neurofibromin is defective and results in the clinical synd...
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Neuron

Neurons are cells of the central nervous system, located within the grey matter, and responsible for all neurological functions of the brain.  Structure Neurons vary in morphology and size substantially, but all share a number of features 1: a cell body nucleus perikaryon: cytoplasm surroun...
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Oligodendrocytes

Oligodendrocytes are one of the four principles types of glial cells and are the central nervous system equivalent of the Schwann cells found peripherally. They wrap the neurons of the brain and spinal cord with myelin 1.  See also oligodendroglioma
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p16

p16 is a widely used immunohistochemical marker indicating expression of the cell cycle protein cyclin-dependent kinase inhibitor 2A, which is upregulated by human papillomavirus (HPV) infection. In the uterine cervix, p16 positivity supports the diagnosis of a high-grade squamous intraepithelia...
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Perivascular pseudorosettes (ependymoma)

Perivascular pseudorosettes are a common histologic feature of central nervous system ependymomas. They represent sections through papillary structures composed of tumor cells arranged radially around a central vessel. Between the central vessel and the tumor cells is a relatively microscopicall...
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Pick bodies

Pick bodies are intracytoplasmic spherical inclusions found in Pick's disease. They are composed of tau fibrils (thus Pick's disease is a tauopathy) arranged in a disorderly array 1. Although tau protein is a major component a number of other protein products are present, including ubiquitin and...
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Picornaviruses

Picornaviruses (pico-RNA-viruses) are non-enveloped, positive-stranded RNA viruses with an icosahedral capsule. Their positive, single stranded RNA architecture places them in Baltimore group IV. The name derives from the fact that they are small (pico) RNA viruses. The picornavirus family cont...
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Poliovirus

Poliovirus is the causative agent involved in poliomyelitis. It is a single-stranded RNA virus and one of the smallest significantly described viruses: group: group IV family: picornaviruses genus: enterovirus species: enterovirus C subtype: poliovirus Related pathology poliomyelitis pol...
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Pregnancy-associated plasma protein-A

Pregnancy-associated plasma protein-A (PAPP-A) is a protein found in the maternal circulation and is produced by the placenta. The PAPP-A gene has been assigned to human chromosome 9q33.1 and contains 22 exons 5. PAPP-A values tend to rise exponentially during pregnancy and the reference range d...
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Primary lung tumors in children

Pediatric primary lung tumors are rare in children however they must be distinguished from locally aggressive inflammatory conditions and benign disease. 1 Primary lung tumors in the neonates and infants include: pleuropulmonary blastoma (PPB) infantile fibrosarcoma of the lung fetal lung in...
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Prostate specific antigen

Prostate specific antigen (PSA) is currently used as a tumor marker for prostate adenocarcinoma. PSA is a 33 kilodalton glycoprotein produced in prostate epithelial cells. Its normal physiologic role is as a liquefying agent for seminal fluid; only a tiny amount leaks into the blood, therefore ...
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Prostate-specific membrane antigen

Prostate-specific membrane antigen (PSMA) (also known as glutamate carboxypeptidase II) is a type II transmembrane glycoprotein that has become an increasingly prominent imaging biomarker 1. PSMA has emerged as a useful target in PET imaging of prostate cancer, especially in the evaluation of sm...
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Proteins

Proteins comprise long chains of amino acids joined together by peptide bonds. Structure A peptide bond is formed by the carboxyl group of one amino acid linking to the amino group of the next one.  Arbitrarily proteins are categorized according to length of the amino acid chain: peptides (2-...
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Pseudocyst

A pseudocyst is an abnormal fluid-filled cavity which is not lined by epithelium.  It is this fact that distinguishes it pathologically from a cyst, which is lined by epithelium. Examples of pseudocysts are: pancreatic pseudocyst pulmonary pseudocyst pseudocysts of the germinal matrix
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Pulmonary Acinetobacter infection

Pulmonary Acinetobacter infection refers to pulmonary infection with Acinetobacter species of which Acinetobacter calcoaceticus-A baumannii complex accounts for a considerable proportion. Pulmonary infection with this organism can cause hospital acquired pneumonia (especially the late onset type...
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Reed-Sternberg cells

Reed-Sternberg cells are a classical finding diagnostic of Hodgkin lymphoma. They are giant, multinucleated cells with abundant pale cytoplasm. Reed-Sternberg cells are rare, making up <1% of lymphoid tissue, with the background consisting of lymphocytes, plasma cells, eosinophils and macrophages.
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Rosenthal fibers

Rosenthal fibers are astrocytic cytoplasmic inclusions, typically found in areas of longstanding gliosis. These elongated or "corkscrew" structures occur within astrocytic processes and are brightly eosinophilic (stain bright pink on the H&E stain) 1-3. They represent astrocytic processes swolle...
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S100

S100 is a family of cytoplasmic calcium-binding proteins expressed in numerous cell lines which can be targeted by immunohistochemistry. Staining for S100 is helpful in characterizing a number of tumors, including malignant melanoma, glial tumors, neurogenic tumors (e.g. schwannomas and neurofib...
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Schiller-Duval body (histology)

Schiller-Duval body is a perivascular structure that can be found in 50% of testicular yolk sac tumors also known as endodermal sinus tumors. If present it is considered pathognomonic.  Pathology A central vessel is surrounded by tumor cells, and the cell-vessel complex is contained in a cysti...
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Selenium

Selenium (chemical symbol Se) is one of the trace elements. It has a vital role in the metabolism of the thyroid hormones and for the functioning of several important enzymes. Chemistry Basic chemistry Selenium has the atomic number 34 with an atomic weight of 78.96 g/mol. It is a non-metal a...
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Senile calcific scleral plaques

Senile calcific scleral plaques, also known as senile scleral plaques (SSP), are benign scleral degenerations common in elderly individuals. They are a common incidental finding on CT imaging. Epidemiology The prevalence of SSP increases with age, from ~2.5% at age 60, to 25% at age 80 years a...
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Sentinel lymph node

Sentinel lymph nodes (SLNs) are defined as those lymph nodes that directly drain a malignancy, or alternatively can be considered as the first node(s) that a tumor metastasizes to. History and etymology "Sentinel node" as the initial draining node of a malignancy was first used in a paper writ...
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Septum (general)

Septa (singular: septum) are anatomical or pathological structures that subdivide an component of normal anatomy or a lesion. In Latin septum means a fence, hence its customary medical usage. Terminology Septa is the plural of the Latin word septum. Septae and septi are erroneous forms and are...
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Sulfur

Sulfur (chemical symbol S) is one of the essential trace elements. It has an important biological role as part of sulfur-containing amino acids and other important biochemical species such as glutathione, hydrogen sulfide, and coenzyme A. Terminology Sulfur has been the preferred spelling of t...
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Synaptophysin

Synaptophysin is a membrane glycoprotein found in presynaptic vesicles and is commonly used as an immunohistochemical marker for cells of neuronal (e.g. gangliogliomas) and neuroendocrine lineage (e.g. pheochromocytomas and paragangliomas) 1,2.  In the brain, it has been suggested that perisoma...
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Tanycytes

Tanycytes are one of the three types of ependymal cells, themselves a type of glial cell. They are found lining the floor of the third ventricle and the median eminence of the hypothalamus 1.   It is believed that these specialized cells are involved in the feedback mechanisms on the anterior p...
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Thyroseq

Thyroseq® is an expanded gene classifier test designed for further evaluation of indeterminate thyroid nodules on fine needle aspiration (FNA). In particular, it is designed to further evaluate nodules that show atypia of undetermined significance / follicular lesion of undetermined significance...
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Tissue tropism

Tissue tropism is a phenomenon by which certain host tissues preferentially support the growth and proliferation of pathogens. This concept is central to the radiological evaluation of infectious disease.  Pathology As infections that display tissue tropism will thrive in certain tissue locati...
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TP53 (gene)

The TP53 gene, located on chromosome 17, is a tumor suppressor gene, responsible for the production of the p53 protein, a transcription regulatory protein which works in concert with a number of other proteins, together forming the p53 pathway 1,2. Inherited mutations in this gene result in the...
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Trace elements

The trace elements are chemical elements which are essential - but only in tiny quantities - for optimal physical and mental well being. The elements are: cobalt copper iodine iron manganese molybdenum selenium sulfur zinc It is now contentious whether chromium is a truly essential tra...
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Tuberculous abscess

Tuberculous abscesses are an uncommon presentation of tuberculosis, most often encountered in immunocompromised individuals (e.g. HIV/AIDS). Unlike the far more common tuberculomas (tuberculous granulomas), tuberculous abscesses contain pus with abundant identifiable organisms 1. The capsule tha...
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Tumor markers

Tumor markers are a group of molecules in serum that are elevated in various malignancies and are often used to monitor treatment response as well as alert for potential progressive disease when in remission. Commonly used markers include: AFP (alpha fetoprotein) beta-hCG CA 15-3 CA 19-9 C...
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Urine

Urine represents the biofluid end-product of the renal filtration process. Normally it is a transparent, sterile, pale-yellow liquid (although clearly color varies with the person's hydration status).  Urine is one of the most easily-accessible biofluids in the human body and has been intensive...
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Verocay bodies

Verocay bodies are a histological feature of schwannomas and represent a particular growth pattern of Antoni type A pattern in which tumor cells form alternating parallel rows of nuclear palisades separated by regions of acellularity 1. 
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Vimentin

Vimentin is a fairly widespread cytoskeletal component encoding for intermediate filaments. It can be used as a target for immunohistochemistry to help characterize numerous tissues and tumors. 
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Vitamin A

Vitamin A (the retinoids) are a group of fat-soluble vitamins required for many physiological functions, mainly vision, reproduction and epithelial maintenance. In the retina, a specific retinoid, 11-cis-retinal, is formed by photoisomerisation within the rods and cones. Related pathology Path...
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Vitamin B1

Vitamin B1 (thiamine) is a water-soluble vitamin, that is part of the vitamin B complex, and is an important coenzyme for two reactions in the citric acid cycle (Kreb cycle). It therefore is vital for cellular ATP production, particularly in the central nervous system. Terminology Thiamine is ...
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Vitamin B12

Vitamin B12 (hydroxocobalamin, hydroxycobalamin or B12a) is a water-soluble vitamin, part of the vitamin B complex, and synthesized by intestinal flora that forms a cobalt-based coenzyme that is required for two vital cellular reactions, namely the production of methionine (an amino acid) and th...
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Vitamin B2

Vitamin B2 (riboflavin) is a water-soluble vitamin, part of the vitamin B complex, that is an important component of the cofactors flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). The flavoproteins contribute to many cellular reactions, including the metabolism of several other...
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Vitamin B3

Vitamin B3 (niacin or nicotinic acid) is a water-soluble vitamin, part of the vitamin B complex, that is an important part of the coenzyme nicotinamide adenine dinucleotide (NAD+) which is involved in many reactions of cellular metabolism. Related pathology pellagra is the clinical syndrome of...
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Vitamin B5

Vitamin B5 (pantothenic acid) is a water-soluble vitamin, part of the vitamin B complex, that is required to synthesize coenzyme A, a very important coenzyme in many cellular metabolic reactions.Vitamin B5 deficiency (hypovitaminosis B5) is extremely rare.
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Vitamin B6

Vitamin B6 is a group of water-soluble vitamins, part of the vitamin B complex, and that are derivatives of pyridine, namely pyridoxine, pyridoxal and pyridoxamine. All three form part of the coenzyme pyridoxal 5'-phosphate (PLP) which is involved in many cellular reactions including the synthes...
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Vitamin B7

Vitamin B7 (biotin) is a water-soluble vitamin, part of the vitamin B complex, and a coenzyme for many reactions, including gluconeogenesis and the synthesis of fatty acids and amino acids. Biotin deficiency is caused by dietary insufficiency, pharmacological interactions, biotinidase deficienc...
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Vitamin B9

Vitamin B9 (folate or folic acid) is a water-soluble vitamin, part of the vitamin B complex, vital for the synthesis of several amino acids, the purines adenosine and guanine and the pyrimidine thymine (three of the four nucleotide bases and hence critical for the synthesis of nucleic acids). T...
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Vitamin C

Vitamin C (ascorbic acid) is a water soluble vitamin that is a coenzyme for the formation of the structure protein collagen, particularly creating cross-linking of collagen fibers which greatly increases its tensile strength. It also acts as an antioxidant. Related pathology Pathological manif...
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Vitamin D

Vitamin D (calciferol) is used to describe a group of five fat-soluble secosteroid vitamins required for the homeostasis of serum calcium and phosphorus. Vitamin D exists in two main forms (vitamers) in humans: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3).  Vitamin D3 acts by re...
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Vitamin E

Vitamin E (the tocopherols) are a group of fat-soluble vitamins that act as antioxidants. hypovitaminosis E is rarely seen outside premature infants hypervitaminosis E is extremely rare as the toxicity of vitamin E is low except in chronic (usually >1 year) high doses. The commonest sequela is...
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Vitamin K

Vitamin K is a family of fat-soluble vitamins essential for normal blood-clotting function and comprises two vitamers that are found naturally: phytomenadione (also known as phylloquinone or K1) and menaquinone (or K2). Menadione is a synthetic molecule which is occasionally called vitamin K3 h...
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Vitamins

Vitamins are a group of organic compounds used in biochemical pathways. Many are components of coenzymes in particular metabolic reactions. Vitamins are generally not synthesized by the human body and hence must be acquired through the diet. Vitamer is the name given to the different forms of a ...
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WHO histological classification of tumors of the uterine cervix

The WHO histological classification is a detailed classification of tumors of the uterine cervix. epithelial tumors squamous tumors and precursors squamous cell carcinoma, not otherwise specified - 8070/3 keratinizing - 8071/3 non-keratinizing - 8072/3 basaloid - 8083/3 verrucous - 8051/3...
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Zinc

Zinc (chemical symbol Zn) is a trace element with a key role as a constituent of enzymes, e.g. carbonic anhydrase, and as part of zinc finger proteins, vital for the correct folding of macromolecules, such as DNA. More recently zinc has been found to act as an important cellular messenger 3. Ba...

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