The 2005 WHO histological classification of odontogenic tumors lays out a classification system for neoplasms and other tumors related to the odontogenic apparatus. At the time of writing (2016), it is still the most widely used classification system although a new revision is due to come up in ...
Endometrial stromal tumors (EST) constitute <2% of all uterine tumors and <10% of uterine mesenchymal neoplasms 1.
Over the past four decades, EST classification has gone through various modifications, starting from the earliest study by Norris and Taylor 2. This was primarily due to the rarit...
3D conformal radiation therapy (3D-CRT) is a radiation therapy technique that involves CT planning where the volume to be treated is defined on a 3D data set. Therefore, organs at risk can also be delineated with the aim of shielding these and reducing treatment side effects. Radiotherapy planni...
A mnemonic for causes of abdominal distension (6 Fs) is:
F: fulminant mass
Acinic cell carcinoma of the lung (also known as a Fechner tumor) is a type of lung carcinoma of the salivary gland type. It is extremely rare, especially when it presents in the form of primary acinic cell carcinoma.
Histologically, they are comprised of clear cells with abundant gr...
An acquired tracheo-esophageal fistula refers to a pathological communication between the trachea and esophagus due to a secondary cause
Acquired causes of tracheo-esophageal fistulae can be divided into those that are related to malignancy (common) and those from other causes (unco...
Acute abdominal pain is a common acute presentation in clinical practice. It encompasses a very broad range of possible etiologies and diagnoses, and imaging is routinely employed as the primary investigative tool in its modern management.
A subgroup of patients with acute abdomina...
Acute airspace opacification with lymphadenopathy is a subset of the differential diagnosis for generalized airspace opacification and includes:
post-obstructive causes (usually chronic, but 'new' changes can occur)
primary lung cancer
Acute lymphoblastic leukemia (ALL) is a malignant disorder of the bone marrow characterized by the proliferation of the lymphoid progenitor cells.
ALL is the commonest form of childhood leukemia, accounting for ~80% of pediatric leukemia cases 1. In adults, ALL corresponds to ~20%...
Acute myeloid leukemia (AML), also referred to as acute myelogenous leukemia, is a hematological malignancy characterized by the abnormal clonal proliferation of immature myeloid precursors (myeloblasts) or poorly differentiated cells of the hematopoietic system. It primary infiltrates the bone ...
Adenocarcinoma in situ, minimally invasive adenocarcinoma and invasive adenocarcinoma of the lung are relatively new classification entities which replace the now-defunct term bronchoalveolar carcinoma (BAC).
In 2011 the International Association for the Study of Lung Cancer (IASLC) and several...
Adenocarcinomas in situ (AIS) of the lung refer to a relatively new entity for a pre-invasive lesion in the lung. This entity partly replaces the noninvasive end of the previous term bronchoalveolar carcinoma. Adenocarcinoma in situ is defined as a localized adenocarcinoma of <3 cm that exhibits...
Adenocarcinoma of the lacrimal glands is rare, with few cases reported in the literature since it was first described in 1996 1. Primary adenocarcinoma of the lacrimal gland is extremely rare; only 9 cases have been reported in the literature 1,2. It can be classified into high- and low-grade ma...
Adenocarcinoma of the lung is the most common histologic type of lung cancer. Grouped under the non-small cell carcinomas of the lung, it is a malignant tumor with glandular differentiation or mucin production expressing in different patterns and degrees of differentiation.
This article brings...
Adenocarcinoma of the urinary bladder is rare and accounts for only ~1% of all bladder cancers (90% are transitional cell carcinomas).
Metaplasia of urinary bladder induced by chronic irritation or infection can lead to adenocarcinoma. Pathological types of adenocarcinoma of the urin...
Adenoid cystic carcinomas are a rare histological subtype of adenocarcinoma.
Adenoid cystic carcinomas are generally considered low grade 4. The tumors have a notable tendency for perineural spread.
They have a wide distribution and mainly occur in relation to the airways,...
Adenoid cystic carcinoma (ACC) of the lung is a type of non-small cell lung cancer. They are classified under lung carcinomas of the salivary gland type. Primary occurrence in the lung parenchyma is rare, while in the thorax they occur more commonly as adenoid cystic carcinoma of the tracheobron...
Adenoid cystic carcinoma (ACC) of the breast is a rare subtype of breast cancer.
They account for only 0.1-0.4% of all breast cancers.
The tumor demonstrates a strikingly characteristic microscopic pattern similar to that of adenoid cystic carcinoma of the salivary gla...
Adenoid cystic carcinoma (ACC) of the salivary glands is the most common malignancy involving the minor salivary glands and the second most common malignancy involving the parotid gland.
Adenoid cystic carcinomas arise more commonly in the minor salivary glands (~55%) than in the maj...
Adenoid cystic carcinomas of the tracheobronchial tree are a type of low-grade tracheal tumor. They are considered to be the second most common primary tumor of the trachea.
They are usually first recognized in patients in their 4th and 5th decades. There is no recognized gender p...
Adenomatoid odontogenic tumors are rare and differ from most other dentition related lesions in that they more frequently occur in the maxilla.
They are also seen more frequently in females, most frequently in the second decade of life.
They present as an e...
Adenosquamous cell carcinoma (ASC) of the cervix is a rare histological subtype of cervical carcinoma.
It has components of both cervical adenocarcinoma and cervical squamous cell carcinoma.
An adenosquamous histology appears to be an independent predictor of poor outcome...
Adenosquamous carcinoma (ASC) of the lung is a rare type of non-small cell lung cancer.
It is thought to constituting 0.4-4% of cases non-small cell lung cancer.
The definition of adenosquamous carcinoma indicates a carcinoma showing components of adenocarcinoma and sq...
Adrenal calcification is not a rare finding in healthy asymptomatic people and is usually the result of previous hemorrhage or tuberculosis. Addison disease patients only occasionally develop calcification.
sepsis: Waterhouse-Friderichsen syndrome
An adrenal collision tumor or collision tumor of the adrenal gland is an uncommon condition where two histologically distinct tumors abut each other or are in close proximity in the same adrenal gland.
Collision tumors have been reported in nearly every organ, for example, collision ...
Primary adrenal cortical carcinoma is a highly malignant but rare neoplasm. It may present as a hormonally active or an inactive tumor.
Although men and women are affected equally, functioning tumors are more common in females, who are also more likely to have an associated endoc...
Adrenal metastases are the most common malignant lesions involving the adrenal gland. Metastases are usually bilateral but may also be unilateral. Unilateral involvement is more prevalent on the left side (ratio of 1.5:1).
They are present at autopsy in up to 27% of patients with ...
Cervical lymphadenopathy in an adult can result from a vast number of conditions. They include:
from head and neck tumors
other neoplastic lesions
Aflatoxins are naturally-occurring mycotoxins that are produced by Aspergillus species, especially Aspergillus flavus. They are acutely toxic and carcinogenic.
High-level aflatoxin exposure can result in acute aflatoxicosis with acute hepatic necrosis, leading to cirrhosis, and ...
Aggressive fibromatosis is a type of musculoskeletal fibromatosis. While it is a non-metastasizing fibrous lesion, it is thought to be a true neoplasm that arises from the fascial and musculoaponeurotic coverings, sometimes at the site of a traumatic or post-surgical scar.
Alveolar soft part sarcomas (ASPS) are rare, highly vascular, deep soft tissue malignancy that is classically seen in the lower extremities of young adults. They account for <1% of all soft tissue sarcomas.
There is a slight female predilection in patients less than 30 years old 1...
Ameloblastomas are locally aggressive benign tumors that arise from the mandible, or, less commonly, from the maxilla. Usually present as a slowly but continuously growing hard painless lesion near the angle of the mandible in the 3rd to 5th decades of life, which can be severely disfiguring if ...
Anal cancer is a relatively uncommon, accounting for less than 2% of large bowel malignancies, and most of the cases are made of squamous cell carcinoma.
It accounts for less than 2% of large bowel malignancies and 1-6% of anorectal tumors (~1.5% of all gastrointestinal tract mal...
Anaplastic lymphoma kinase (ALK) fusion oncogene positive non small cell lung cancer refers to a specific set of non small cell lung cancers that contain an inversion in chromosome 2. They are associated with specific clinical features, including never or light smoking history, younger age, and ...
Anaplastic thyroid cancer staging refers to TNM staging of anaplastic thyroid carcinomas. Papillary, follicular, and medullary thyroid carcinomas are staged separately. The following article reflects the 8th edition manual published by the American Joint Committee on Cancer, which is used for st...
The anatomy curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core anatomy knowledge for radiologists and imaging specialists.
Head and neck anatomy
Abdominal and pelvic anatomy
Breast angiosarcomas are a rare vascular breast malignancy.
As primary tumors of the breast, they account for ~0.04% 2 of all breast cancers and tend to occur in younger women, in their 3rd to 4th decades.
Secondary angiosarcoma, related to prior therapy of breast cancer, has an ...
The Ann Arbor staging system is the landmark lymphoma staging classification system for both Hodgkin lymphoma and non-Hodgkin lymphoma.
It is named after the town of Ann Arbor in the US state of Michigan where the Committee on Hodgkin's Disease Staging Classification met in 1971 to agree on it...
Germ cell tumors are one of the causes of anterior mediastinal mass, and any of the germ cell histologies may be identified. They can therefore be divided histologically into:
non-seminomatous germ cell tumors (NSGCT)
embryonal cell carcinoma
yolk sac tumor
Getting a film with an anterior mediastinal mass in the exam is one of the many exam set-pieces that can be prepared for.
The film goes up and after a couple of seconds pause, you need to start talking:
There is a left sided mediastinal mass that makes obtuse angles with the mediastinal c...
Apocrine carcinoma of the breast is a rare variant of breast cancer. The diagnosis is mainly pathological as it is difficult to differentiate from other forms of breast cancer on imaging.
It accounts for about 4% of all cases. It is seen most often in females in the age group of 5...
Appendiceal mucoceles occur when there is an abnormal accumulation of mucin causing abnormal distention of the vermiform appendix due to various neoplastic or non-neoplastic causes.
The reported prevalence at appendectomy is 0.2-0.3%. They are thought to typically present in middl...
The apple core sign, also known as the napkin ring sign (bowel), is most frequently associated with constriction of the lumen of the colon by a stenosing annular colorectal carcinoma.
The appearance of the apple-core lesion of the colon also can be caused by other diseas...
Asbestosis refers to later development of diffuse interstitial fibrosis secondary to asbestos fiber inhalation and should not be confused with other asbestos related diseases.
Asbestosis typically occurs 10-15 years following the commencement of exposure to asbestos and is dose re...
The original description of the Askin tumor (by Askin and Rosai in 1979 1), and many studies following it have led to a great deal of confusion. Until recently it has been considered a separate entity or as a type of peripheral primitive neuroectodermal tumor, usually of the chest wall.
Assessment of thyroid lesions is commonly encountered in radiological practice.
hyperplastic / colloid nodule / nodular hyperplasia: 85%
papillary: 60-80% of carcinomas
Asymmetrical mammographic density, or more simply asymmetries, is a spectrum of morphological descriptors for a unilateral fibroglandular-density finding seen on one or more mammographic projections that does not meet criteria for a mass.
The criteria for an asymmetry includes that it is seen o...
Atypical ductal hyperplasia (ADH) is a histologically borderline lesion that has some, but not all the features of ductal carcinoma in situ (DCIS). Sometimes the distinction between ADH and DCIS is simply on the basis of the number of ducts involved.
Atypical ductal hyperplasia is a...
Atypical teratoid/rhabdoid tumors (AT/RT) are an uncommon WHO Grade IV tumor, which in the vast majority of cases occurs in young children less than two years of age. It most frequently presents as a posterior fossa mass. AT/RT often resembles medulloblastoma by imaging and even H&E microscopy, ...
BALT lymphoma is an abbreviated term for bronchus-associated lymphoid tissue lymphoma. These neoplasms fall under the broader umbrella of mucosa associated lymphoid tissue (MALT) lymphomas. It is sometimes considered a type of primary pulmonary lymphoma.
Up to half of pat...
Bat's wing or butterfly pulmonary opacities refer to a pattern of bilateral perihilar shadowing. It is classically described on a frontal chest radiograph but can also refer to appearances on chest CT 3-4.
Bat's wing pulmonary opacities can be caused by:
Benign and malignant characteristics of breast lesions at ultrasound allow the classification as either malignant, intermediate or benign based on work published by Stavros et al. in 1995.
Malignant characteristics (with positive predictive values)
There are a number of benign metastasizing tumors:
benign metastasizing meningioma 1,2
benign metastasizing leiomyoma 3
primary adenoma of thyroid 4
giant cell tumor of bone 5
Beta-hCG (bHCG or β-hCG) is a sex hormone found in the mother's blood serum that can be used to help interpret obstetric ultrasound findings.
Beta-hCG levels may be used in three ways in the clinical setting of pregnancy:
qualitatively, for presence/absence of fetal tissue
more often determin...
The Bethesda criteria are an alternative to the Amsterdam criteria for the clinical diagnosis of hereditary non-polyposis colorectal cancer (HNPCC).
Diagnosis of HNPCC is made if any of the following criteria are fulfilled:
Amsterdam criteria are met
2 or more HNPCC related malignancies
Bilateral testicular lesions have a relatively limited differential diagnosis.
lymphoblastic leukemia (acute or chronic)
primary testicular lymphoma is rare but the testes are often the site of lymphoma/leukemia recurrence due to ...
Bing-Neel syndrome is an extremely rare neurological complication of Waldenström macroglobulinemia where there is malignant lymphocyte infiltration into the central nervous system (CNS).
The exact incidence is unknown, however in one study of patients with Waldenström macroglobuli...
Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematological malignancy. It was previously termed as blastic natural-killer lymphoma or agranular CD4+ natural killer cell leukemia.
It only represent a very small proportion (~0.44%) of all hematological malignancies...
There are several bony lesions that can involve or produce a sequestrum.
Brodie abscess: osteomyelitis
certain soft tissue tumors (with bony extension)
malignant fibrous histiocytoma
metastasis (especially from breast ca...
Normal bone marrow is divided into red and yellow marrow, a distinction made on the grounds of how much fat it contains.
Red marrow is composed of:
reticulum (phagocytes and undifferentiated progenitor cells)
scattered fat cells
a rich v...
Mnemonics to help remember common causes of bony sequestrum include:
E: eosinophilic granuloma
I: infection (Brodie abscess)
L: lymphoma (skeletal)
M: malignant fibrous histiocytoma or metastasis (especially from breast carcinoma)
Borderline ovarian serous cystadenomas lie in the intermediate range in the spectrum of ovarian serous tumors and represent approximately 15% of all serous tumors.
They present at a younger age group 1-2 than the more malignant serous cystadenocarcinomas with a peak age of present...
Brachytherapy, also known as sealed source radiotherapy or endocurietherapy, is a form of radiotherapy where a radioactive source is placed, under the guidance of imaging, within or next to the area requiring treatment.
Brachytherapy has been used to treat:
breast cancer (ofte...
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: ...
Brain metastases are estimated to account for approximately 25-50% of intracranial tumors in hospitalised patients. Due to great variation in imaging appearances, these metastases present a common diagnostic challenge which can importantly affect the management approach for individual patients.
Common brain tumors in infancy (i.e. under one year of age) are quite different from those of brain tumors in adulthood. Most are located in the supratentorial region (~65%) and they carry a poor prognosis.
The frequency of these tumors varies according to studies, but the most common brain tum...
A breast abscess is a relatively rare but significant complication of mastitis that may occur during breastfeeding, particularly in primiparous women. The clinical context is a key to diagnosis as imaging appearances (particularly ultrasound) can mimic many other entities such as breast carcinom...
Breast architectural distortion is a descriptive term in breast imaging (mammography, ultrasound, and MRI) to indicate that the breast parenchyma is tethered or indented. The finding per se is not a mass.
Architectural distortion is often due to a desmoplastic reaction in which there...
This is a basic article for medical students and other non-radiologists
Breast cancer is the commonest malignancy in female patients.
This is a summary article; read more in our article on breast cancer.
1 in 4 cancer deaths in women worldwide 1
BI-RADS (Breast Imaging-Reporting and Data System) is a risk assessment and quality assurance tool developed by American College of Radiology that provides a widely accepted lexicon and reporting schema for imaging of the breast. It applies to mammography, ultrasound, and MRI. This article refle...
A BI-RADS 4 lesion under the breast imaging reporting and data system refers to a suspicious abnormality. BI-RADS 4 lesions may not have the characteristic morphology of breast cancer but have a definite probability of being malignant. A biopsy is recommended for these lesions. If possible, the ...
Breast implant-associated anaplastic large cell lymphoma (BIA-ALCL) is a rare form of T-cell primary breast lymphoma which has primarily been associated with textured breast implants.
The entity is rare, with a prevalence of 1 in 1,000 to 1 in 10,000 women with breast implants 8...
Breast lymphoma refers to the involvement of the breast with lymphoma and may be primary or secondary.
Both primary and secondary breast lymphomas are rare. Breast lymphoma accounts for <1% of all breast malignancies and <2% of all extranodal non-Hodgkin lymphoma 11. Secondary lym...
Breast MRI is the most sensitive method for detection of breast cancer. Depending on international health regulations, it is either applied for screening of women at high risk for developing breast cancer (e.g. BRCA1 and BRCA2 carriers), as an additional diagnostic test in pretherapeutic breast ...
Breast neoplasms consist of a wide spectrum of pathologies from benign proliferations, high risk lesions, precursor lesions, to invasive malignancies. This article provides an overview for radiologists, with a focus on breast cancer. For a summary article for medical students and nonradiologist...
Breast sarcoma refers to a relatively heterogenous group of rare breast tumors which can include:
angiosarcoma of the breast
pleomorphic sarcoma of the breast
fibrosarcoma of the breast
myxofibrosarcoma of the breast
leiomyosarcoma of the breast
primary osteosarcoma of the breast
The bright rim sign, also known as the hyperintense ring sign, has been described in dysembryoplastic neuroepithelial tumors (DNET). It is described as a well defined rim of high signal around the DNET on FLAIR sequences. This T2/FLAIR hyperintense ring, whether complete or in complete, is fair...
British Thoracic Society guidelines for pulmonary nodules were published in August 2015 for the management of pulmonary nodules seen on CT. In the United Kingdom, they supersede the Fleischner Society guidelines.
They are based initially on identifying whether the nodule is solid or subsolid an...
A mnemonic to remember diseases that undergo bronchovascular spread is:
K: Kaposi sarcoma
I: infection (e.g. pneumocystis pneumonia, tuberculosis)
L: lymphangitis carcinomatosis
The ultrasound "U" classification of thyroid nodules has been developed by the British Thyroid Association (BTA) as part of their 2014 guidelines on the management of thyroid cancer 1.
It allows for stratifying thyroid nodules as benign, suspicious or malignant based on ultrasound appearances t...
Bulging duodenal papilla is a conical or cylindrical protuberance at the medial aspect of the descending or horizontal duodenum at the site of the sphincter of Oddi. It is finding on small bowel follow-though (and endoscopy) and has a relatively long differential. On cross-sectional imaging, th...
Burkitt lymphoma is an aggressive B-cell lymphoma predominantly affecting children.
Burkitt lymphoma is the most common (40%) type of non-Hodgkin lymphoma in childhood. Median age is eight years with a male predominance (M:F = 4:1) 1. It is less common in adults, accounting for 1-...
CA-125 is a high-molecular-weight glycoprotein found on the surface of Mullerian and coelomic 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 be...
Carcinoma antigen 15-3, usually shortened to 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.
MUC-1 is a normal epithe...
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...
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 ...
In order of decreasing frequency, a useful mnemonic to remember glial tumors which calcify is:
Old Elephants Age Gracefully
There are numerous causes of calcified mediastinal lymph nodes.
Common causes include:
infectious granulomatous diseases
Uncommon causes include:
Pneumocystis jiroveci (PCP) pneumonia
thyroid carcinoma: papi...
Calcifying fibrous tumors, previously known as calcifying fibrous pseudotumors, are rare, benign fibroblastic tumors of the soft tissues.
It can occur at all ages and there is no strong gender predilection 1. Fewer than 200 cases have been reported in the English literature 1.
A useful mnemonic to remember the causes of calcifying pulmonary metastases is:
B: bone (chondrosarcoma, osteosarcoma)
A: any primary post-chemotherapy
Cancer staging involves a number of systems to help direct treatment and aid prognosis. The AJCC TNM staging schema is the most common, but other systems are used for specific malignancies or body parts.
breast cancer staging
lung cancer staging
malignant pleural mesothelioma s...
Cannonball metastases refer to large, well circumscribed, round pulmonary metastases that appear, well, like cannonballs. The French term "envolée de ballons" which translates to "balloons release" is also used to describe this same appearance.
Metastases with such an appearance are classically...
Carcinoid heart disease, also known as Hedinger syndrome, is a known complication of carcinoid tumors, and is particularly prevalent in patients who develop carcinoid syndrome.
Cardiac lesions are present in approximately 50% of patients with carcinoid syndrome 1.