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.

49 results found
Article

Acanthosis nigricans

Acanthosis nigricans is a cutaneous disorder characterized by symmetric hyperpigmented velvety plaques on the neck, axillae, antecubital and popliteal fossae, inframammary, and groin areas. It is associated with acquired lipodystrophy. Pathology The benign form of acanthosis nigricans is assoc...
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RNA

RNA (ribonucleic acid) is one of the two major nucleic acids in biological cells, the other being DNA; unlike DNA, RNA is single-stranded. The composition of the nucleotides and nucleosides is also partly different due to variations in the monosaccharide and base constituents: D-ribose sugar rep...
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CSF alpha-fetoprotein

Alpha-fetoprotein (AFP) in the cerebrospinal spinal fluid (CSF) has been reported as a tumor marker for some intracranial tumors with yolk sac elements, and teratoma 1. Interpretation Elevation intracranial yolk sac tumor intracranial embryonal carcinoma congenital CNS tumors with yolk sac ...
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Immunosuppression

Immunosuppression is the impairment of the body's immune system which can alter the ability of the body's defense mechanisms to prevent diseases, particularly certain infections, including opportunistic infections, and cancers.  Terminology Patients with immunosuppression are said to be immuno...
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Alcian blue stain

Alcian blue stain is a histological stain utilized for the identification of extracellular matrix proteoglycans, like glycosaminoglycans and hyaluronic acid 1, commonly in connective tissue and epithelial malignant neoplasms 2, and also Barrett esophagus, where it can highlight mucosal intestina...
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Giemsa stain

Giemsa stain is a commonly used histological stain that colors the cytoplasm blue to pink (depending on its acidity) and the nucleus blue to black 1. It serves as the diagnostic gold standard of histopathological staining of blood samples from patients with plasmodium-borne malaria, and as the b...
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Neoplasm

Neoplasms, also known as tumors, are pathological masses, caused by cells abnormally proliferating and/or not appropriately dying. Neoplasms may be either benign or malignant. Malignant neoplasms are synonymous with cancers. Benign neoplasms clear origin (unless very large) slow growth  usua...
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Prostatic acid phosphatase

Prostatic acid phosphatase (PAP) also known as prostatic specific acid phosphatase (PSAP) is an enzyme generated by prostatic glandular tissue. Usage It can be used in immunohistochemistry to identify prostatic tissue including prostatic epithelium and prostatic ducts and is usually expressed ...
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DNA

DNA (deoxyribonucleic acid) is a nucleic acid that encodes the genetic information (genome) necessary for RNA (ribonucleic acid) transcription (transcriptome) and protein synthesis (proteome) 1. It is contained in the nucleus of eukaryotic cells in the form of chromatin or chromosomes 7,8. Mole...
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Bethesda classification system for thyroid fine needle aspirates

Bethesda classification system for thyroid fine needle aspirates comprises six categories of pathological reporting of thyroid FNA, with each category linked to a malignancy risk. Classification category I: non-diagnostic category II: benign category III: atypia of undetermined significance...
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Lepidic growth

Lepidic growth is a pathological term referring to a pattern of cell proliferation along the lining of the alveolar structures of the lung as is seen in a subset of lung tumors 1. History and etymology ‘lepidic’ was coined by the English pathologist John George Adam (1862-1926) whilst at McGil...
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Nucleic acids

The nucleic acids are the collective term for the two main macromolecular nucleotide polymers: DNA (deoxyribonucleic acid) RNA (ribonucleic acid) Nucleotides, the constituent units of nucleic acids, are made up of simpler molecules called nucleosides and inorganic phosphate (H3PO4). Each nucl...
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Metachronous (pathology)

The term metachronous is used in oncology to refer to two (or more) independent primary malignancies, when the second (or third, etc.) malignancy arose more than six months after the diagnosis of the first malignancy 1,2. These may be in the same, or in different, organs. See also synchronous ...
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Synchronous (pathology)

The term synchronous is used in oncology to refer to two (or more) independent primary malignancies, when the second (or third, etc.) malignancy arose within six months of the diagnosis of the first malignancy 1,2. These may be in the same, or in different, organs. See also metachronous multi...
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Hamartoma

A hamartoma (plural: hamartomas or hamartomata) is a benign tumor-like malformation that consists of a collection of architecturally disorganized cells located in an area of the body where the cells are normally found. It is often due to abnormal development. In radiology, hamartomas often mimi...
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Desmoplasia

Desmoplasia (also known as a desmoplastic reaction) is the term used by pathologists to refer to the growth of fibrous tissue around disease, usually cancer. However in dermatopathology, desmoplasia may also be seen with benign, as well as malignant, conditions. Terminology Pathologists prefer...
Article

mTOR protein

The mTOR proteins, an abbreviation for mammalian target of rapamycin, also known as mechanistic target of rapamycin, are two proteins that are involved in cell signaling pathways implicated in tumorigenesis. The mTOR proteins are serine/threonine protein kinases that combine with several other ...
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ROS1 mutation

The ROS1 mutation is a mutation occurring in the ROS1 oncogene on chromosome 6 resulting in a defective receptor tyrosine kinase which has structural similarity to the anaplastic lymphoma kinase (ALK) protein. It is thought to be present in several cancers of the subtype non-small cell lung can...
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Well differentiated fetal adenocarcinoma of lung

A well-differentiated fetal adenocarcinoma (WDFA) of lung is a rare low grade lung tumor. Some consider this as a variant of adenocarcinoma with others considering this under the group of pulmonary blastomas 5.  According to classification by the World Health Organization in 1999, it was remove...
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Vascular invasion in lung cancer

Vascular invasion in lung cancer is one of the invasive patterns that can occur in lung cancer. Dependent on the publication, this could mean: intratumoral vascular invasion (IVI)  microscopic vascular invasion (MVI) lymphovascular invasion (LVI) lymphatic permeation arterial invasion veno...
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Tumor spread through air spaces

Tumor spread through air spaces (STAS) is a relatively recently recognized pattern of invasion in lung adenocarcinoma. According to the 2015 WHO classification, STAS is defined as “micropapillary clusters, solid nests, or single cells spreading within air spaces beyond the edge of the main tumor...
Article

HER-2 mutations in lung cancer

Human epidermal growth factor receptor 2 (HER-2) mutations may be detected in approximately 3% of lung adenocarcinomas 1. Radiographic features CT Early studies have suggested HER2-mutant tumors exhibit more aggressive features in general and tend to: exhibit a locally-invasive behavior comp...
Article

KRAS mutation

KRAS (shortened name for the gene Kirsten RAt Sarcoma viral oncogene homolog) mutations are associated in a number of malignancies including:  certain adenocarcinomas of the lung colorectal carcinoma 1 pancreatic ductal adenocarcinoma Several germline KRAS mutations have also been found to b...
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EGFR mutation

An epidermal growth factor receptor (EGFR) mutation may be expressed in a large proportion of non-small cell lung carcinomas (NSCLC). However, certain subtypes such as invasive mucinous adenocarcinoma of the lung can have very low expression. The presence of this mutation can be assessed on bio...
Article

Anaplastic lymphoma kinase (ALK) gene rearrangements

Anaplastic lymphoma kinase (ALK) gene rearrangements are known to occur in association with several tumors. The genes code for an enzyme called anaplastic lymphoma kinase (ALK) or ALK tyrosine kinase receptor (also known as CD246) which is thought to play a role in brain development and exerts i...
Article

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...
Article

Lactate dehydrogenase

Lactate dehydrogenase (LDH or LD) is a key enzyme in most cells, catalyzing the reversible conversion of pyruvate to L-lactate. Its contemporaneous main clinical uses are limited primarily to the investigation of hemolysis, serous collections and as a tumor marker. Physiology L-lactate dehydro...
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Extranodal extension

Extranodal extension refers to the growth of a nodal cancer metastasis beyond the confines of the capsule of a lymph node into adjacent tissues. Less preferred synonyms include extranodal spread, extracapsular extension, or extracapsular spread. This finding holds prognostic implications. For e...
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CA 15-3

CA 15-3 is a tumor marker used in monitoring breast cancer. The test detects levels of MUC-1, a mucin protein in the blood. MUC-1 is thought to be important in the invasiveness and metastasization of cancer cells. Physiology Mucin-1 is a normal epithelial cellular glycoprotein localized to the...
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Sentinel lymph node

The 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 ...
Article

Elevated vitamin B12 (marker)

Elevated vitamin B12 (also known as hypervitaminosis B12 or hypercobalaminemia) is most important as a diagnostic and prognostic marker for malignant disease 1,3. Very high serum levels of vitamin B12, following dietary megadosing, does not seem to have any observable deleterious effects 2. 
Article

CA 27-29

CA 27-29 is a tumor marker and is a soluble form of glycoprotein MUC1. It may be elevated in patients with breast cancer. Tumors of the colon, stomach, kidney, lung, ovary, pancreas, uterus, and liver may also raise CA 27-29 levels. Certain non-malignant conditions are also associated with its ...
Article

Malignant transformation

Malignant transformation is the term given to the process whereby either normal, metaplastic, or benign neoplastic tissue, becomes a cancer. The process usually occurs in a series of steps and the affected tissue gradually accumulates the genetic mutations that express a malignant phenotype. The...
Article

Exophytic

Exophytic is a descriptive term used by radiologists/pathologists to describe solid organ lesions arising from the outer surface of the organ of origin. Literally exophytic only refers to those lesions arising from the outer surface, however radiologists and pathologists use the term to include...
Article

Radiogenomics

Radiogenomics is a relatively recently coined term to denote the relationship between the imaging features of a particular disease and various genetic or molecular features. The former is referred to as an imaging phenotype, whereas the later as genomic phenotype.  Radiogenomics, therefore, pro...
Article

PSA density

The PSA density (PSAD), is a calculation performed at diagnosis and is the serum prostate specific antigen (PSA) level (ng/mL) divided by the volume of the prostate gland (mL), resulting in a value with the units, ng/mL2 1. Prostate volume is calculated from TRUS measurements 2,3.  Alternativel...
Article

CDKN2A/p16

CDKN2A (cyclin-dependent kinase inhibitor 2A) is a tumor suppressor gene that encodes for the p16 protein, involved in the CDK4/6–RB1 cell-cycle pathway 5.  p16 is a widely used immunohistochemical marker indicating expression of the cell cycle protein, which is upregulated by human papillomavi...
Article

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...
Article

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...
Article

BRAF

BRAF (B-Raf proto-oncogene serine/threonine-protein kinase) is a proto-oncogene, encoding for a serine/threonine protein kinase. Mutations of BRAF are the most common alteration of the RAS/MAPK pathway and these have been identified in a variety of tumors and congenital syndromes including 1-5: ...
Article

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 ...
Article

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...
Article

CEA

Serum CEA (carcinoembryonic antigen) is a cell-adhesive glycoprotein that was discovered in colorectal cancer in 1965, and is hence one of the oldest and most used tumor markers. Its name derives from its normal expression in fetoembryonic liver, gut and pancreas tissue. Normal range of CEA is ...
Article

Circumferential resection margin

Circumferential resection margin (CRM) is a term used to denote the standard plane of excision of total mesorectal excision, used for resection of rectal cancers. The anatomic correlate is the mesorectal fascia. The distance between tumor tissue or satellite tumor deposits and the mesorectal fas...
Article

CA 19-9

CA 19-9 (carbohydrate antigen 19-9 or cancer antigen 19-9) is a serum antigen (monosialoganglioside) that has increased diagnostic use in the management of several malignancies, mainly of hepatopancreaticobiliary origin. It is non-specific, however, and can rise in both malignant and non-maligna...
Article

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...
Article

CA-125

CA-125 is a high-molecular-weight glycoprotein found on the surface of Müllerian and celomic epithelial-derived cell types and is the best known tumor marker for epithelial ovarian cancer 6. Importantly, it may also be elevated in several other conditions (see differential diagnosis section belo...
Article

Myo-inositol peak

Myo-inositol 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).  Myo-inositol is a precursor of both phosphatidylinositol (the major inositol-containing phospholipid) and phosphatidylinos...
Article

WHO classification of odontogenic and maxillofacial bone tumors

The WHO classification of odontogenic and maxillofacial bone tumors, last published in 2017, is a subset of the WHO classification of head and neck tumors (4th edition), which lays out a histological classification system for neoplasms and other tumors related to the odontogenic apparatus. Clas...

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