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.

142 results found
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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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Pneumatosis cystoides intestinalis

Pneumatosis cystoides intestinalis s a radiographic/descriptive entity characterised by the presence of multiple gas-filled cysts in the submucosa and/or gastrointestinal subserosa of the small intestine. It is a subtype of pneumatosis with specific features, which can occur anywhere along the g...
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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 intracranial leiomyosarcoma

Primary intracranial leiomyosarcomas are primary malignant tumours derived from smooth muscle cell lineage in the cranial vault. Epidemiology Primary intracranial leiomyosarcomas are extremely rare. Most commonly, these lesions have been described as EBV associated smooth muscle tumours in pat...
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Primary lung tumours in children

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

Prostate specific antigen (PSA) is currently used as a tumour 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 categorised 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 account for a considerable proportion. Pulmonary infection with this organism can account for hospital acquired pneumonia (especially the late onset...
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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 fibres

Rosenthal fibres 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 targetted by immunohistochemistry. Staining for S100 is helpful in characterising a number of tumours, including malignant melanoma, glial tumours, neurogenic tumours (e.g. schwannomas and neur...
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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 tumours also known as endodermal sinus tumours. If present it is considered pathognomonic.  Pathology A central vessel is surrounded by tumour cells, and the cell-vessel complex is contained in a cy...
Article

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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Selenium deficiency

Selenium deficiency (or hyposelenaemia) when severe may present with arthritic and cardiac-related symptoms.  Epidemiology Up to one billion people globally are thought to have some degree of selenium deficiency. Phenylketonuria patients are more likely to experience selenium deficiency as ma...
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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...
Article

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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Shoulder injury related to vaccine administration

Shoulder injury related to vaccine administration (SIRVA) describes the injury that occurs when there is an unintentional injection of antigenic material in the synovial tissues resulting in an inflammatory reaction. Clinical presentation After a vaccine administration, mostly on the first day...
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Sideroblastic anaemia

Sideroblastic anaemia (also known as sideroachrestic anaemia) is a rare cause of anaemia characterised by the presence of ring sideroblasts rather than normal red blood cells in the bloodstream. Sideroblastic anaemia is either congenital or acquired. Clinical presentation Symptoms and signs re...
Article

Spindle cell lipoma

Spindle cell lipoma is a benign lesion in which mature fat is replaced by collagen-forming spindle cells.1,2 Epidemiology Spindle cell lipoma typically present in the middle aged to elderly men between the ages of 45 and 65 years.1,2 Clinical presentation Spindle cell lipoma has a significan...
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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 specialised cells are involved in the feedback mechanisms on the anterior p...
Article

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 tumour 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 th...
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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 fluoride iodine iron manganese molybdenum selenium sulfur zinc It is now contentious whether chromium is a truly ess...
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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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Tumour markers

Tumour 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 19-9 CA 27-29 ...
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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 colour varies with the person's hydration status).  Urine is one of the most easily-accessible biofluids in the human body and has been intensiv...
Article

Verocay bodies

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

Vimentin

Vimentin is a fairly widespread cytoskeletal component encoding for intermediate filaments. It can be used as a target for immunohistochemistry to help characterise numerous tissues and tumours. 
Article

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...
Article

Vitamin B1

Vitamin B1 (thiamine) is a water-soluble vitamin that 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. Related pathology Pathological manifestations only occur with t...
Article

Vitamin B12

Vitamin B12 (hydroxocobalamin, hydroxycobalamin or B12a) is a water-soluble vitamin synthesised 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 the metabolism of odd-number carbon at...
Article

Vitamin B2

Vitamin B2 (riboflavin) is a water-soluble vitamin 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 vitamins.  Isolated deficiency...
Article

Vitamin B3

Vitamin B3 (niacin or nicotinic acid) is a water-soluble vitamin 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 niacin deficiency, and may affe...
Article

Vitamin B5

Vitamin B5 (pantothenic acid) is a water-soluble vitamin that is required to synthesise coenzyme A, a very important coenzyme in many cellular metabolic reactions.Vitamin B5 deficiency (hypovitaminosis B5) is extremely rare.
Article

Vitamin B6

Vitamin B6 is a group of water-soluble vitamins 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 synthesis of several amino acids and the me...
Article

Vitamin B7

Vitamin B7 (biotin) is a water-soluble vitamin that is 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 deficiency and, possibly, increased b...
Article

Vitamin B9

Vitamin B9 (folate or folic acid) is a water-soluble vitamin that is 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). The antimicrobial drug cl...
Article

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 fibres which greatly increases its tensile strength. It also acts as an antioxidant. Related pathology Pathological manif...
Article

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...
Article

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...
Article

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 synthesised by the human body and hence must be acquired through the diet. Vitamer is the name given to the different forms of a ...
Article

WHO histological classification of tumours of the uterine cervix

The WHO histological classification is a detailed classification of tumours of the uterine cervix. epithelial tumours squamous tumours and precursors squamous cell carcinoma, not otherwise specified - 8070/3 keratinizing - 8071/3 non-keratinizing - 8072/3 basaloid - 8083/3 verrucous - 805...

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