Differentiating benign from malignant pulmonary nodules is of great importance as it determines the further course of management of the patient.
Benign pulmonary nodule
size: the smaller the size the more likely to be benign
~80% of benign nodules are <2 cm in size.
margin: smooth, regular; ...
Breast leave alone lesions are so characteristic on mammography that further diagnostic tests such as a biopsy are unnecessary. All of these lesions are entirely benign and known as BI-RADS 2 findings:
lipoma: fat density; well-defined rounded lesion
oil cyst: fat density; well-defined lesion;...
Edematous breast refers to the thickening of skin and Cooper's ligaments of the breast with increased parenchymal density on mammography, which causes a coarse reticular pattern. Findings could be unilateral or bilateral, and regarding the presence or absence of inflammation/erythema, differenti...
Decreased duodenal folds may be seen on imaging modalities, particularly MR enterography, and differential diagnoses include:
scleroderma - usually with duodenal dilatation
celiac disease - particularly involves the distal duodenum and jejunum
Nontoxic megacolon refers to colonic dilatation of more than 6 cm in an adult without mural abnormality. This is in contrast to toxic megacolon, an acute complication accompanied by mural abnormalities such as thickening, loss of haustral folds, pneumatosis or free gas.
The differential diagnos...
The central scar in hepatic lesions most frequently has been described in focal nodular hyperplasia which the scar is T2 hyperintense and usually non-calcified, and fibrolamellar hepatocellular carcinoma, where the scar is T2 hypointense and often calcified. Scars do not have to be exactly centr...
Bowel wall fat deposition refers to the infiltration of the submucosa with fat and usually occurs in chronic processes such as inflammatory bowel disease, causing characteristic fat halo sign on CT images.
Other differential diagnoses include:
normal variant - particularly in obese patients w...
Bowel wall calcification is not common and can occur secondary to various mechanisms due to benign, premalignant, or malignant lesions.
The differential diagnoses include:
gastrointestinal stromal tumor (GIST)
metastatic calcification - due to renal failure
Thymic calcifications are rare findings usually associated with thymoma but are also seen in other pathologies.
thymoma - more frequent in invasive thymoma 1
multilocular thymic cyst 2
anterior mediastinal amyloidosis 3
Bilateral hypertranslucent hemithoraces is the presence of decreased density of the hemithoraces bilaterally on a plain chest radiograph. This hypertranslucency, a.k.a. hyperlucency, may be focal or diffuse 1.
Also see unilateral hypertranslucent hemithorax.
Apical chest masses are often important and may be missed, especially when examined with a plain chest radiograph. It is always recommended to perform a targeted assessment of the apices of the lungs during a chest x-ray; they are one of the classic review areas.
Submandibular gland enlargement refers to an increase in the volume of the submandibular gland, exceeding "normal" values of 7.4 ± 1.8 mL 1.
submandibular duct stenosis (e.g. tumor, granulomatous disease)
acute sialadenitis: following ...
Finger pathology is wide and includes all lesions involving the tendons, ligaments, muscles, bone, and articulations of the hand and foot digits.
brachydactyly - short digits
brachymetatarsia - short metatarsal
arachnodactyly - elongated, thin "spider-like" digits 1
Hypovascular retroperitoneal lesions are those which do not enhance in the late arterial and portal venous phases on CT. Some of these lesions may show progressive enhancement in the delayed phase due to their fibrous or myxoid matrix components.
Hypervascular retroperitoneal lesions are findings that enhance avidly in the late arterial phase with or without washout in the portal venous and delayed phases, on contrast-enhanced CT or MRI.
Early enhancement with slow washout
Reflux of contrast into inferior vena cava can be common findings seen on CT. It is considered a specific but insensitive sign of right-sided heart disease / right heart dysfunction at low contrast injection rates although the usefulness decreases with high injection rates.
Penile calcifications are a relatively rare finding. The commonest cause is Peyronie disease.
penile calciphylaxis (considered by some to be a form of calcinosis cutis)
penile urethral calculus
calcinosis cutis of the penis
idiopathic calcinosis cutis o...
Symmetrical cerebral T2/FLAIR hyperintensities are seen in a broad range of pathologies. The differential depends essentially on the location of the lesions.
Symmetrical corticospinal tract lesions
amyotrophic lateral sclerosis
symmetrical T2/FLAIR hyperintensities along the corticospinal tra...
Cerebellar restricted diffusion refers to a hyperintense signal involving the cerebellum on DWI images with a corresponding low signal on ADC images.
Vascular thrombo-occlusive disease
cerebellar arterial infarction 1
superior cerebellar arterial infarct
Fluid-fluid levels in liver lesions are a rare appearance of both benign and malignant conditions.
complicated hepatic cyst 2
hepatic abscess 2
chronic hepatic hematoma 3
biliary cystadenoma 3
hepatic hemangioma (very rare) 2
Uterine restricted diffusion refers to a hyperintense signal involving the endometrium, myometrium, or cervix on DWI images with a corresponding low signal on ADC images, with a mean cut-off ADC value for malignancy of 1.15 x 10-3 mm2/s 7.
Endometrial restricted diffusion
Hypervascular splenic lesions are findings that enhance more or similarly to the background splenic parenchyma on late arterial phase, on contrast-enhanced CT or MRI.
splenic hemangioma 2
most common primary benign neoplasm of the spleen
second most com...
Per vaginal (PV) bleeding in a non-pregnant patient is a common clinical presentation with a multitude of causes.
The potential causes vary with the patient's menstrual status. A well-known mnemonic is found here.
Periportal lymphadenopathy can be a common observation during imaging of the upper abdomen. What is considered the exact upper limit of normal has been variable 1,3 among different publications but with many authors suggesting a cut-off of around 10 mm in short axis diameter.
Optic nerve calcification is a rare radiological finding, with only a short differential diagnosis, many of which have only been described in isolated case reports 1-4.
optic nerve meningioma
optic nerve head drusen
idiopathic dural optic nerve sheath calcification
A mnemonic to remember differentials causing diffuse bone marrow infiltration on MRI. Bone marrow infiltration is best evaluated on T1 sequences and may be focal or diffuse. Focal infiltration is seen in metastases and lymphoma. The diffuse pattern is seen more commonly in multiple myeloma, mast...
Spinal epidural cystic lesions are fluid-filled lesions within the spinal canal but outside the thecal sac. Their clinical significance is as a potential contributor to spinal cord or nerve root impingement. Simple appearing spinal epidural cysts may represent several entities that differ by ori...
Hypervascular pancreatic lesions are findings that enhance more or similarly to the background pancreatic parenchyma in the late arterial phase, on contrast-enhanced CT or MRI.
intrapancreatic accessory spleen: should not be overdiagnosed as a malignant tumor
The presence of gas in the pancreatic gland and/or the pancreatic ducts is an uncommon finding.
Causes of gas in the pancreatic ducts
altered function and/or anatomy of the sphincter of Oddi: causes duodenal-pancreatic duct reflux
patulous pancreatic duct opening 2
Renal emphysema, or intrarenal gas, refers to the presence of gas within the kidney, with or without extension to the urinary tract.
It is a rare finding and only a few differentials need to be considered 1:
emphysematous pyelonephritis 1
Intraosseous gas, also known as osseous pneumatosis, refers to the accumulation of gas bubbles within the cortical bone, trabecular bone, the bone marrow, or in the medullary cavity.
Intraosseous gas is an uncommon finding and differentials include 1,2:
Maxillodental leave alone lesions are usually incidental findings that do not require treatment nor follow-up if the patient is asymptomatic.
This article includes findings from orthopantomogram, cone-beam CT, and sinus CT studies.
Do not touch:
Leave alone lesions of the skull base refers to incidental findings that do not require treatment nor follow-up.
This article includes findings from brain CT, HRCT of the temporal bone, and MRI studies.
Do not touch:
arrested pneumatization of the skull base - sphenoid benign fatty lesion 1
Leave alone lesions are findings that are usually discovered incidentally and do not require any specific treatment or follow-up if the patient is asymptomatic.
This article includes findings from paranasal sinus CT and MRI studies.
Bilateral temporal lobe T2 hyperintensity refers to hyperintense signal involving the temporal lobes on T2 weighted and FLAIR imaging. It is a common finding on brain MRI and a wide range of differentials should be considered 1.
Cerebral cortical calcification or gyral calcification refers to curvilinear calcifications involving the cerebral cortex.
ischemic stroke sequelae
congenital cerebral toxoplasmosis
congenital cytomegalovirus infection
Cerebral cortical T1 hyperintensity or gyriform T1 hyperintensity refers to curvilinear hyperintense signal involving the cerebral cortex on T1-weighted images on brain MRI.
accumulation of denatured proteins and/or lipid-laden macrophages
cortical laminar necrosis 2
Cerebral cortical T2 hyperintensity or gyriform T2 hyperintensity refers to curvilinear hyperintense signal involving the cerebral cortex on T2 weighted and FLAIR imaging.
The causes include:
focal cortical dysplasia
Cerebral cortical restricted diffusion or gyriform restricted diffusion refers to curvilinear hyperintense signal involving the cerebral cortex on DWI images with a corresponding low signal on ADC images.
Vascular thrombo-occlusive disease (most common) 1
Bilateral pleural effusions can be common in general radiology practice. They may be symmetrical or asymmetrical. They can occur from several varied etiologies although congestive heart failure (CHF), renal or liver failure are generally considered common 1.
Recognized list of causes are many...
Differential diagnoses of cirrhotic liver nodules include regenerative liver nodules, dysplastic liver nodules, and hepatocellular carcinoma (HCC), all represent a spectrum of diseases ranging from non-neoplastic reparative process (regenerative) to nuclear atypia (dysplastic) to typical neoplas...
Epiglottic enlargement is often seen on lateral neck radiographs and it's accepted to confirm clinical suspicion of acute epiglottitis only on this finding 1. However, an enlarged epiglottitis has a wide range of differentials that should be considered.
Ureteral calcification refers to the presence of calcium concretions within the ureteral lumen or wall.
transitional cell carcinoma
schistosomiasis of the urinary tract
Intracranial fat is uncommon and a wide range of differentials should be considered.
intracranial dermoid cyst
quadrigeminal cistern lipoma
suprasellar cistern lipoma
cerebellopontine angle lipoma
choroid plexus li...
Optic canal enlargement can be caused by numerous etiologies.
The optic canal has an average transverse diameter of 3.6 ± 0.6 mm 1. The optic canal can be considered enlarged when it is >6.5 mm in transverse diameter 4.
glioma of optic nerve
meningioma of optic nerve shea...
Hemithoracic volume loss can occur from a number of situations. These include:
pulmonary hypoplasia (unilateral)
isolated unilateral pulmonary artery agenesis
skeletal deformities - e.g. kyphosis,
Infection in childhood
Mass-forming chronic pancreatitis occurs in around 30% of cases of chronic pancreatitis, where a mass or a focal enlargement of the pancreas is usually seen on imaging. In many instances, it poses a challenge as the epidemiology and imaging appearances overlap those of pancreatic adenocarcinoma....
Giant cell carcinomas of the lung are a rare type of non-small cell lung carcinomas (NSCLC) classified under sarcomatoid carcinomas of the lungs.
They represent less than 0.5% of all NSCLC 2. There is a recognized association with smoking 1.
Symptoms are n...
Bronchial stenosis, or bronchial strictures, are descriptive terms to denote regions of focal narrowing involving the bronchi. They can arise from a wide variety of etiologies.
It can arise from a large range of etiological factors, which include:
A duodenal stricture refers to a segment of narrowing involving the duodenum. They can occur from a range of benign infective - inflammatory to malignant etiology. They can contribute to gastric outlet obstruction.
Isolated diffuse ground-glass opacification/opacity (GGO) has a relatively well-defined differential diagnosis although this remains broad and clinical correlation, like many respiratory diseases, is key to diagnosis.
Miller et al. have described the following different...
Only a small number of pulmonary diseases are known to directly traverse the lung fissures such that the lung pathology extends from one lobe via the interlobar fissure into an adjacent lobe 1. The finding is most commonly due to primary malignancy, however, some infections are also known to do ...
Vacuum phenomena describe aseptic gas collections (e.g. nitrogen and traces of oxygen and or carbon dioxide) within different specific tissues 1-3. Usually, they are seen within the intervertebral discs, the bones and within different joints, but can also be seen in other usually adjacent locati...
Cavernous sinus gas locules can be seen in several settings.
iatrogenic pneumocephalus secondary to gas embolism (especially venous gas embolism) from IV access (can be a relatively common finding in the absence of direct trauma and does not require treatment).
traumatic pneumocephalus: in the...
Disconnected pancreatic duct syndrome, also referred only as disconnected pancreatic duct, refers to the symptoms and complications due to the complete discontinuity of the main pancreatic duct between segments of viable secreting pancreatic tissue and the duodenum, usually seen as a sequela of ...
High-risk pregnancies are any that actually or potentially threaten either the health or life of the mother or her fetus during pregnancy, labor, or birth. From a radiological perspective, high-risk pregnancies may undergo further screening or have close follow-up with growth and well-being scan...
Abnormal testicular Doppler flow (arterial, venous, or both) can be a differential challenge. Always remember that the patient's presenting history helps quite a bit in narrowing the differential.
partial testicular torsion (<360 degrees)
venous outflow is obstructed first, resul...
Esophageal wall thickening can be observed in a number of situations and can be either focal or diffuse. It may be physiological, and can also be due to benign or malignant disorders.
diffuse esophageal spasm
forms of esophagitis
diffuse esophageal intramural hemat...
Hyperattenuating pulmonary consolidation refers to a region of lung parenchyma with air space opacification that has higher attenuation on CT than muscle or than expected with typical causes of consolidation such as pneumonia (fluid attenuation) or cancer (soft tissue attenuation).
Gyral enhancement, also known as gyriform, cortical, or grey matter enhancement, is a pattern of contrast enhancement in the superficial brain parenchyma that conforms to the serpentine morphology of the cerebral gyri. It should be distinguished from leptomeningeal enhancement, which is also ser...
Diffuse airway narrowing can occur from a number of pathologies; these include:
granulomatosis with polyangiitis
various infections including
Intrahepatic arteriovenous shunts, also referred to as intrahepatic arteriovenous malformations (AVMs) or hepatic arteriosystemic venous shunts, represent a spectrum of abnormal communications between the hepatic arterial system and the hepatic veins.
Please note that arterioportal shunts, whi...
Non-cardiogenic pulmonary edema is a classification of pulmonary edema where the underlying etiology is not due to left ventricular dysfunction. Causes include:
pulmonary edema with acute asthma
post-obstructive pulmonary edema/postintubation pulmonary edema/negative pressure ...
Retrorectal developmental cysts are rare and mostly congenital benign lesions found in the retrorectal space:
spectrum of cystic teratomas
retrorectal epidermoid cyst
retrorectal dermoid cyst
retrorectal teratoid cyst
duplication cyst of the rectum
tailgut duplication cyst
Snowsport injuries cover a broad range of activities from skiing and snowboarding to recreational play (e.g. tobogganing, tubing).
Snowsports are popular with over 70 million people globally participating each year 1. While the injury rate varies depending on location, a rough ave...
Periapical radiolucencies are commonly observed findings on OPG and other dental/head and neck imaging modalities.
They can represent a number of pathologies:
periapical lucency related to apical periodontitis
Calcific cervical lymphadenopathy is uncommon and has a limited differential diagnosis, including malignant and benign etiologies. The most frequent causes include 1:
malignancies (more common)
metastatic thyroid carcinoma (most common; papillary or medullary types) 2,5
Lacrimal sac masses are very uncommon and more commonly have a malignant (~80%) rather than benign (~20%) etiology.
granulomatosis with polyangiitis
Fat containing cardiac lesions have a limited differential diagnosis. These include 1-4:
normal aging/physiologic: mostly subepicardial, more in the right ventricle (especially right ventricular outflow tract) than left ventricle
lipomatous hypertrophy of the interatrial septum
Intra-articular gas or air (pneumarthrosis) can occur from a number of varied pathologies and should be interpreted according to the clinical context.
compound injury with gas entering from the outer surface
can occur with a pneumolipohaemarthrosis
Hepatosplenomegaly is simply the simultaneous presence of a pathologically-enlarged liver (hepatomegaly) and spleen (splenomegaly).
Many infections can produce a mild concurrent enlargement of the liver and spleen. This list is by no means exhaustive.
Gallbladder cancer is relatively uncommon compared to other hepatobiliary malignancies.
gallbladder adenocarcinoma: most common 1
gallbladder squamous cell carcinoma
gallbladder neuroendocrine carcinoma
gallbladder sarcoma: very rare 2
Cardiac calcification is a broad term for any calcification affecting the valves, coronary arteries, aortic root, endocardium, myocardium, and/or pericardium.
Causes of cardiac calcification are:
coronary artery disease (most common)
coronary artery aneurysms, e.g. in Kawasaki dise...
Band like structures in the gestational sac is not an uncommon finding in the first trimester or second trimester ultrasound scans and can represent a number of varying conditions
Mastoid air cell opacification can occur in a number of situations and can include a spectrum of inflammatory, neoplastic, vascular, fibro-osseous, and traumatic changes.
Possible causes include:
trauma (temporal bone f...
Coarse trabecular bones can result from a number of causes 1,2:
Paget disease (bone)
hemaglobinopathies, e.g. thalassemia, chronic iron deficiency anemia 3
coarse trabecular pattern in bone (mnemonic)
Linear atelectasis (plural: atelectases), and also known as discoid, plate or band atelectasis, refers to a focal area of subsegmental atelectasis that has a linear shape. Linear atelectasis may appear to be horizontal, oblique or perpendicular and is very common. It usually occurs as a conseque...
Compressive atelectasis refers to a form of lung atelectasis due to compression by a space-occupying process.
Some authors describe it as a subtype of passive (relaxation) atelectasis where the reduction in lung volume is greater than its normal relaxed state 1. Whereas others describe it as th...
Lobar consolidation is the term used to describe consolidation in one of the lobes of the lung. It infers an alveolar spread of disease and is most commonly due to pneumonia.
Consolidation refers to the alveolar airspaces being filled with fluid (exudate/transudate/blood), cells (inf...
Right upper lobe consolidation refers to consolidation in part (incomplete) or all (complete) of the right upper lobe.
Consolidation refers to the alveolar airspaces being filled with fluid (exudate/transudate/blood), cells (inflammatory), tissue, or other material.
The list of caus...
Overhead elbow sports injuries are a group of pathologies seen in sports activities with overhead throwing or strokes, e.g. tennis, volleyball, baseball, javelin throwing. There has been a tremendous increase in the number of participants in these sports activities worldwide.
Gamuts in radiology refer to the complete list of differential diagnoses for any radiological finding. We include gamut as a section for articles on Radiopaedia.org.
History and etymology
According to Maurice Reeder, writing in the preface of his own eponymous text on gamuts, it was the trailb...
Epiphora (plural: epiphoras) represents excessive tearing of the eye and is a common clinical presentation to ophthalmological practice. It is most frequently due to an obstruction of the nasolacrimal drainage apparatus. Less commonly, overproduction of tears may be responsible.
Peribronchovascular thickening is a broad imaging descriptive term commonly used to describe thickening of any one or more of the below:
peribronchovascular interstitial thickening
bronchial wall thickening: can be differentiated from true peribronchovascular thickening on cross-sectional imag...
Secondary organizing pneumonia (SOP) refers to organizing pneumonia that can be attributed to a specific cause, in contrast to cryptogenic organizing pneumonia (COP) in which no cause is present.
Secondary organizing pneumonia can be attributed to the following causes 1:
Reeder and Felson's Gamuts in Radiology, first published in 1975, provided comprehensive lists of radiological differential diagnoses, or gamuts, and was a bestseller for many years. The current publisher is Springer.
The first edition was edited and, primarily, written by Ben Felson and Mauric...
Maurice "Mo" M Reeder (1933-2013) was an American radiologist who is remembered for his contributions to radiology education in the United States, in particular, the development of the radiology-pathology teaching program at the Armed Forces Institute of Pathology.
Maurice Merrick R...
Chronic suppurative lung disease (CSLD) refers to a group of conditions which includes:
primary ciliary dyskinesia
This term is usually used in the context of pediatric patients.
Some medical conditions are characterized by the presence of pathological gas i.e. gas/air found in a space, tissue, or organ, where it would not normally be expected to be.
the prefix "pneumo" is common, especially when it refers to gas within a body space/cavity, e.g. pneumothora...
Nerve root enhancement is a phenomenon described on post-contrast MRI scans that can be observed in a number of situations.
post-operative nerve root enhancement 6
disseminated spinal leptomeningeal metastases
Pediatric nasal cavity masses can occur within the nose or the nasopharynx. These masses are often found incidentally on imaging but can be readily apparent clinically.
The clinical features of these lesions tend to mimic upper respiratory processes and may result in dela...
Here is a list of some of the most useful differential diagnoses in musculoskeletal imaging.
lucent/lytic bone lesions (FEGNOMASHIC)
multiple lucent/lytic bone lesions
benign lytic bone lesions in patients under 30 years old
diffuse bony sclerosis
permeative process in bone
The differential diagnosis for a dense base of the skull includes:
Van Buchem disease