Mediastinal mass differential diagnosis

Mediastinal mass Microchapters
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Overview
Anatomy of Mediastinum
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Differentiating Mediastinal Mass from other Diseases

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Trusha Tank, M.D.[2]

Overview

The mediastinum is a non-delineated group of structures in the thorax (chest), surrounded by loose connective tissue. It is the central compartment of the thoracic cavity. It contains the heart, the great vessels of the heart, esophagus, trachea, thymus, and lymph nodes of the central chest. A wide variety of diseases involving mediastinal structures may present as a mediastinal mass or widening of the mediastinum on imaging studies. Mediastinal widening is diagnosed by the mediastinum measuring greater than 8 cm in width on PA chest x-ray. The mediastinal mass may present with symptoms or even without any symptoms. Mediastinal mass may cause a variety of symptoms by the mass pressing against surrounding mediastinal structures, collectively known as mediastinal syndrome. Mediastinal may can be differentiated depending on their location in mediastinal cavity into: Anterior mediastinal mass, middle mediastinal mass, or posterior mediastinal mass. Mediastinal mass may also be differentiated according to the content of the mass such as: cystic, fatty or solid (tumor).

Mediastinal Mass Differential Diagnosis

Wide variety of medical conditions can present as a mediastinal mass on radiological imaging.

• Mediastinal mass may cause obstruction, entrapment or infiltration of other mediastinal organs such as: trachea, bronchi, esophagus, aorta, superior vena cava (SVC), or heart.
• Symptoms caused by any kind of mediastinal mass is collectively known as: Mediastinal syndrome
• Mediastinal syndrome includes:
  • Symptoms caused by compression of the trachea: Dyspnea and respiratory insufficiency.
  • Symptoms caused by compression of the esophagus: Dysphagia.
  • Symptoms caused by compression of SVC causes superior vena cava syndrome: Vein distention, edema of the face or upper extremities and a positive Pemberton's sign.
    • Pemberton's sign: Development of suffusion, plethora, or duskiness upon elevation of the arms above the head in patient
    • Superior vena cava syndrome is the most severe complication of mediastinal syndrome and a medical emergency.

ABBREVIATIONS: N/A: Not available, SOB: Shortness of breath, M/C: Most common, RI: Respiratory insufficiency, NM: Neuromuscular system, SVCS: Superior vena cava syndrome, SLE: Systemic lupus erythematosus disease, T3: Triiodothyronine, T4: Thyroxine, TSH: Thyroid stimulating hormone, TFT: Thyroid function test, MRI: Magnetic resonance imaging, CNS: Central nervous system, CSF: Cerebrospinal fluid, FNA: Fine needle aspiration, CBC: Complete blood count, COPD: Chronic obstructive pulmonary disease, AIDS: Acquired immune deficiency syndrome, HIV: Human immunodeficiency virus, Hep C: Hepatitis C virus, HTLV-1: human T-lymphotropic virus, EBV: Epstein Barr virus, HHV-8: Human herpes virus-8
Disease	Causes/risk factors	Clinical presentation				Paraclinical findings
		General symptoms	Mediastinal syndrome
			Dyspnea/ RI	Dysphagia	SVCS	Gold standard	Image	Additional findings
Anterior mediastinal mass
Tumors
Thymoma	Human foamy virus Epstein-Barr virus Human T-cell lymphotropic virus MEN 1 syndrome	Cough wheezing Chest pain Muscle weakness (MG) Anemia	+	+	+	Biopsy: Epithelial cells Immature lymphocytes Immature T cells	CT scan showing presence of voluminous expansive lesion of 6 cm in the upper anterior mediastinum without infiltration of surrounding tissues signs with modest enhancement. Case courtesy of Dr. Domenico Nicoletti (Picture courtesy: Radiopedia)	Associated condition Neuromuscular Myasthenia gravis Neuromyotonia Rippling muscle disease Polymyositis/dermatomyositis Encephalitis (limbic, cortical and brainstem) Intestinal pseudoobstruction Hematological Anemia: pure red cell aplasia, pernicious anemia, hemolytic anemia, aplastic anemia Other isolated cytopenias: eosinophils, basophils neutrophils Immunodeficiencies: hypogammaglobulinemia/- T-cell deficiencies (Good syndrome) Dermatological Pemphigus (foliaceus or paraneoplastic) Lichen planus Alopecia areata Endocrine Addison disease Grave's disease Cushing's disease Hepato-renal Glomerulonephritis Autoimmune hepatitis Systemic autoimmune diseases SLE Sjögren's syndrome Systemic sclerosis Graft-versus-host disease
Disease	Etiology	Symptoms	Dyspnea/ RI	Dysphagia	SVCS	Gold standard	Image	Additional findings
Fatty mass	Steroid use Cushing's syndrome Obesity	Mostly asymptomatic	-	-	-	MRI: Well-defined encapsulated mass Extensive fat content Small amounts of solid areas Fibrous septa	Limited images of an MRI of the chest demonstrate the mass to be of fat density. Case courtesy of A.Prof Frank Gaillard (Picture courtesy: Radiopedia)	Fatty mass can be: Lipoma Liposarcoma Thymolipoma
Non-Hodgkin lymphoma	Age (above 60 years) Caucasians > African and Asian Americans Positive family history of first degree relative B-cell activating autoimmune disorders Radiation exposure Infections (HIV, Hep C, HTLV-1, EBV, HHV-8, H. pylori, psittacosis, Campylobacter jejuni) Previous cancer treatment Exposure to chemicals and drugs (pesticides, methotrexate, TNF inhibitors, trichloroethylene) Cigarette smoking for ≥ 40 years BMI ≥30 kg/m2 Diet Hair dyes Breast implants	Painless lymphadenopathy Fever Weight loss and anorexia Night sweats Constant fatigue Itchy skin Cough Shortness of breath Abdominal pain or swelling Constipation Nausea Vomiting Headache Personality changes Seizures	+/-	+/-	+/-	Excisional lymph node biopsy with immunohistochemical study CD 20+ cells	CT scan showing large anterior mediastinal mass. This is most likely lymphoma. Moderate pericardial effusion. Case courtesy of A. Prof Frank Gaillard (Picture courtesy: Radiopedia)	Anemia: Involvement of bone marrow Autoimmune hemolysis and bleeding Thrombocytopenia, leukopenia, or pancytopenia Lymphocytosis with malignant cell Thrombocytosis
Disease	Etiology	Symptoms	Dyspnea/ RI	Dysphagia	SVCS	Gold standard	Image	Additional findings
Hodgkin's lymphoma	Epstein-Barr virus A history of infection with the Epstein-Barr virus (EBV) Family history First-degree relatives Siblings of the same sex HIV infection HIV infection increases risk Autoimmune diseases Rheumatoid arthritis Systemic lupus erythematosus Ulcerative colitis Immune thrombocytopenic purpura Sarcoidosis Immunodeficiency Severe combined immunodeficiency (SCID) Hypogammaglobulinemia Hyperimmunoglobulin M syndrome Congenital immunodeficiency Organ transplant or allogeneic bone marrow transplant Tobacco smoking	Painless lymphadenopathy with a rubbery consistency Systemic B symptoms: Fever (Pel-Ebstein fever): persistent temperature >38°C (>100.4°F) Night sweats Weight loss >10% within the past 6 months Other Pruritus Fatigue Mass effect Chest pain Cough Pain or fullnessbelow the ribs due to swollen spleen or liver Pain in lymph nodes after drinking alcohol Skin blushing or flushing Bone pain	+	+	+/-	Lymph node biopsy with immunohistochemistry Reed-Sternberg cells CD15 and CD30 +	CT scan showing A large soft tissue attenuation mass occupying the anterior mediastinal displaying homogeneous attenuation with low-density areas of cystic changes inside. It extends to the middle mediastinum to occupy the pretracheal space and involve the right hilum. Inferiorly it is inseparable from the anterior pericardium. Compression upon the SVC and encasement of the aorta and great vessels are noted. There is also mild right costal pleural thickening and enhancement suggesting infiltration with mild pleural effusion and abdominal retrocaval lymph nodes. Case courtesy of Dr. Ahmed Abdrabou (Picture courtesy: Radiopedia)	Positron emission tomography (PET) Detect small deposits Monitor the response to treatment Detect recurrences Measure the size of lymph nodes with precision Assess for bone marrow involvement
Mediastinal germ cell tumor (Non-teratomatous)	Exclusively in males 20s - 40s age	Chest pain Cough Wheezing Stridor Weight loss Fever Night sweats	+	-	-	Biopsy may help differentiate histopathological subtypes including: Yolk sac tumor Endodermal sinus tumor Embryonal carcinoma Choriocarcinoma Mixed germ cell tumor	CT scan showing A large heterogeneous anterior mediastinal mass, pathologically shown to be a germ cell tumor. Case courtesy of Radswiki (Picture courtesy: Radiopedia)	CT scan: Homogenous appearance Hemorrhage and coagulation necrosis Metastasis to lymph nodes and bone Non-seminomatous germ cell tumors present as large masses with marked heterogeneous attenuation Invasion of adjacent structures and distant metastasis Pleural and pericardial effusion Laboratory finding: AFP and ß-hCG levels
Teratoma	Benign equal in men and women Malignant more common in men Pediatric population higher risk	Benign Asymptomatic Malignant Cough Chest pain Trichoptysis	+/-	+/-	+/-	Chest CT scan: Location Metastasis Intrinsic structure Soft tissue Fat Calcification	CT scan showing A large teratoma in anterior mediastinum. Case courtesy of Dr. Gagandeep Singh (Picture courtesy: Radiopedia)	N/A
Disease	Etiology	Symptoms	Dyspnea/ RI	Dysphagia	SVCS	Gold standard	Image	Additional findings
Cystic mass
Thymic cyst	Congenital Unilocular Acquired Multilocular: Teratoma Lymphoma Thymic carcinoma Autoimmune disorders	Asymptomatic	-	-	+	Biopsy with histopathology and cytology	CT scan showing A thymic mass corresponds to a cystic lesion. Case courtesy of Dr. Stefan Ludwig (Picture courtesy: Radiopedia)	CT scan: Oval shape Smooth contour Midline location Calcified Septate cyst Fluid attenuation
Thyroid gland disease
Mediastinal goiter	Iodine deficiency Female gender Age over 50 years Personal or family history Certain medications Immunosuppressants Antiretrovirals Amiodarone Lithium Radiation	Swelling at the base of your neck Tight feeling in throat Cough Hoarseness Fatigue	+	+	-	Radioactive iodine scan: Nodules Size Function of the gland: ↑ hyperthyroidism, ↓ hypothyroidism or normal (euthyroid)	CT scan showing A goitrous left lobe 9 cm in its greatest dimension (craniocaudal) extending posterior to the great vessels, 3.4cm below the top of the manubrium. The tracheal axis is shifted to the right and about 2cm below the cricoid cartilage, the trachea is compresssed for a length of 5cm, causing approx. 40% tracheal lumen cross sectional narrowing. Case courtesy of Dr Varun Babu Picture courtesy: Radiopedia)	Hyperactive gland (hyperthyroid): Grave's disease Hypoactive gland (hypothyroid): Hashimoto thyroiditis Normal functioning gland (euthyroid): Benign thyroid enlargement (non toxic multinodular goiter)
Disease	Etiology	Symptoms	Dyspnea/ RI	Dysphagia	SVCS	Gold standard	Image	Additional findings
Middle mediastinal mass
Cardiovascular Disease
Pericardial effusion	Acute myocardial infarction Aortic dissection Aortic rupture Myocardial rupture Rupture of ventricular aneurysm Uremic pericarditis Rheumatic pericarditis Tuberculous pericarditis Uremic pericarditis Viral pericarditis Dressler's syndrome Cardiac catheterization Cardiomyopathy Chemotherapy Chest trauma Collagen vascular disease Congestive heart failure Neoplasm Postpericardiotomy syndrome Postirradiation	Chest pain The positional change affecting the chest pain Orthopnea Fever Symptoms of infection, injury or systemic disease causing the effusion	+	+/-	-	Echocardiography guided pericardiocentesis: Therapeutic Diagnostic Pericardial disease Hemodynamic parameters Volume Effusion content (blood/exudate/transudate) Microbial culture	CT scan showing pericardial effusion is evident (increased fluid-density around the heart) and this is the cause of the enlarged cardiac silhouette on chest x-ray. Numerous axillary and mediastinal lymph nodes. Case courtesy of A.Prof Frank Gaillard (Picture courtesy: Radiopedia)	Physical findings: Pulsus paradoxus Hypotension in cardiac tamponade Jugular venous distension with a prominent Y descent Kussmaul's sign EKG: Electrical alternans Echocardiography: Presence of effusion Reversal of RA and RV diastolic transmural pressures Cardiac chamber indentation or collapse Respiratory variation of atrioventricular valves increased
Aortic dissection	Atherosclerosis Chest trauma Chronic hypertension Complication of cardiac procedures Connective tissue disorders Vasculitis Advanced age Smoking Dyslipidaemia Cocaine Connective tissue disorders	Severe acute chest pain Back pain Pain radiating to neck, throat, jaw, and/or unilateral face Abdominal pain Claudication Hemoptysis Horner syndrome Oliguria/ Anuria Paraplegia, paralysis Hoarseness	+	+/-	+	MRI: Location of the intimal tear Involvement of branches of aorta Other vascular pathology	CT scan showing dilatation of aortic root, ascending aorta, aortic arch and descending aorta. An intimal flap is seen extending from the aortic root proximally to below the origin of the renal arteries distally dividing the aortic lumen into true and false lumens . Case courtesy of Dr Prashant Mudgal (Picture courtesy: Radiopedia)	TEE: Identify true and false lumens Intimal flap Thrombosis in the false lumen Pericardial effusion Aortic regurgitation Proximal coronaries CTA: Beak sign: An acute angle between the dissection flap and the arterial wall Aortic cobwebs: Fibroelastic bands Size: False lumen larger than the true lumen Displaced intimal calcification: True lumen
Disease	Etiology	Symptoms	Dyspnea/ RI	Dysphagia	SVCS	Gold standard	Image	Additional findings
Superior vena cava obstruction	Compression of SVC from: Aortic aneurysm Bronchogenic carcinoma Breast cancer Cystic hygroma Goiter Histoplasmosis Indwelling catheter Lung cancer Lymphoma Non Hodgkin's lymphoma Small cell lung cancer Thymoma Tuberculosis	Cough Hoarseness Chest pain Problems swallowing and/or talking Hemoptysis Headache Dizziness Decreased alertness Dizziness Fainting Sensation of head or ear "fullness" Vision changes	+	+	++	Contrast-enhanced CT scan: Location and severity of the obstruction Superimposed thrombosis Mediastinal mass or lymphadenopathy Collateral vessels and associated lung masses	CT scan showing a large right upper lobe mass abuts the right brachiocephalic vein and SVC. Case courtesy of Dr Henry Knipe (Picture courtesy: Radiopedia)	Invasive contrast venography: Etiology of obstruction Exact location of the obstruction
Partial anomalous pulmonary venous connection	Uncommon congenital abnormality Associated with an ASD Turner's syndrome (monosomy X) The scimitar syndrome	Asymptomatic Exertional dizziness Neck pain Diaphoresis	+	-	-	MRI with contrast: Provide better anatomic definition Associated defects Condition of heart chambers	CT scan showing the anomalous origin of the right subclavian artery. traversing behind esophagus as it crosses midline from left to right. Case courtesy of Dr Piyush P Siwach (Picture courtesy: Radiopedia)	Associated with Adult onset pulmonary arterial hypertension (PAH) Right ventricular volume overload (RV failure) Cardiac catheter: Pressure and O2 Sat in heart chambers PFT: Normal despite of severe SOB
Gastrointestinal tract disease
Esophageal achalasia	Idiopathic Chagas disease Gastric carcinoma Herpes zoster HSV-1 Measles virus Paraneoplastic syndrome Sarcoidosis	Dysphagia for solids and liquids Regurgitation of undigested food Cough Aspiration Weight loss Chest pain, radiate to the back, jaw, neck, and arms Heartburn Hiccup Difficulty belching	+	+	-	High resolution manometry (HRM): Residual pressure of LES > 10 mmHg Incomplete relaxation of the LES Increased resting tone of LES Aperistalsis High intra-esophageal pressure (due to stasis of food)	CT scan showing uniform dilatation of the esophagus with air-fluid level. Patchy consolidation in the upper segment of the right lower lobe likely due to aspiration. Case courtesy of Dr Hani Salam (Picture courtesy: Radiopedia)	X ray: "Bird's beak image" or "rat tail" appearance Dilated esophageal body Air fluid level due to absent peristalsis Absence of gastric air bubble In advanced achalasia - sigmoid appearance CT scan: Dilatation of the esophagus Air fluid levels Exclude pseudoachalasia Achalasia symptoms resulting from esophageal cancer
Disease	Etiology	Symptoms	Dyspnea/ RI	Dysphagia	SVCS	Gold standard	Image	Additional findings
Esophageal cancer	Age over 60 Male gender Smoking Alcohol consumption Obesity Lye ingestion Nitrosamine in food Plummer-Vinson syndrome Tylosis or Howel-Evans syndrome Radiation therapy GERD Barrett's esophagus Achalasia	Dysphagia to solid food Heartburn Weight loss Changes in diet Anorexia Regurgitation of food or saliva Hoarseness or loss of voice Intractable cough Blood in stools Frequent pneumonia	-	+	-	Endoscopy with biopsy: Friable lesion Superficial plaques Nodules Ulcerations Strictures Ulcerated mass Circumferential masses	CT scan showing irregular circumferential thickening of the mid oesophagus with oesophageal dilatation of the proximal segment, invasion of the adjacent right pleura, periosteal reaction without definite invasion of the right 2nd and 3rd ribs, subcarinal lymph node and multiple bilateral metastatic pulmonary nodules Case courtesy of Dr Ahmed Abdrabou (Picture courtesy: Radiopedia)	Barium swallow: Tapering stricture known as a "rat's tail" Irregular stricture Pre-stricture dilatation Shouldering CT scan: Eccentric or circumferential wall thickening >5 mm Peri-esophageal soft tissue and fat stranding Dilated fluid and debris filling the esophageal lumen Tracheobronchial invasion Aortic invasion
Esophageal rupture	Seizures Severe straining Vomiting Childbirth Prolonged coughing or laughing	Mackler's triad: Chest pain Vomiting Subcutaneous emphysema Other: Odynophagia Fever Tachypnea Tachycardia Cyanosis, and hypotension Pleural effusion Patients with cervical perforations can present with Neck pain Dysphonia	+	+	-	Esophagogram: The location Extent of perforation	CT scan showing extensive pneumomediastinum and fluid in the mediastinum. Proximal oesophagus is air-filled and distended to the level of T7 and after this it is largely collapsed. Moderate sized bilateral pleural effusions and a small right apical pneumothorax. Severe centrilobular emphysema. Case courtesy of RMH Core Conditions (Picture courtesy: Radiopedia)	CT scan: Esophageal wall edema and thickening Peri-esophageal fluid Mediastinal widening Air and fluid in the pleural spaces, retroperitoneum, or lesser sac
Hiatus hernia	50 or older age Obesity Female > Male Trauma: when undergoing surgery Frequent coughing Straining with constipation Heavy lifting Congenital Smoking Stress	Nausea Vomiting Regurgitation Heart burn Regurgitation Dysphagia	-	+	-	High resolution manometry with esophageal pressure topography (EPT): Evidence of separation of the crural diaphragm from the lower esophageal sphincter(LES) Real-time localization of the gastroesophageal junction Identification of intermittent herniation	CT scan shows herniation of stomach into the thorax through the hiatus with displacement of gastro-oesophageal junction. Case courtesy of DrDrsmail Kabakus (Picture courtesy: Radiopedia)	Ultrasound: Location of gastroesophageal junction Bowel diameter measured at the diaphragmatic hiatus Ultrasound in pediatric population: Measurement of intra-abdominal esophagus which is less than 2 cm in diameter Sign of a beak at the gastroesophageal junction CT scan: Retrocardiac air-fluid level Organs within the hernia sac Focal fat collection in the middle of the mediastinum Visualise contents, length, orientation of herniated stomach inside the lower thorax Herniated contents lie adjoining to the esophagus Widening of esophageal hiatus Dehiscence of diaphragmatic crura (>15 mm)
Disease	Etiology	Symptoms	Dyspnea/ RI	Dysphagia	SVCS	Gold standard	Image	Additional findings
Pulmonary disease
Hilar lymphadenopathy	Lymphadenopathy: Tuberculosis Tubercular hilar lymphadenopathy in adult particularly in immunocompromised (HIV infection) Bronchogenic carcinoma Lymphoma Sarcoidosis Infection (fungal, atypical mycobacteria, viral, tularemia, and anthrax) Exposure to silica and certain drugs	Constituitional symptoms like: Fatigue Fever Malaise Flu-like illness Nausea and vomiting Night sweats Weight loss and Cachexia	+	-	-	Lymph node biopsy and histopathology	CT scan shows bi-hilar lymphadenopathy and reticulonodular infiltrates. Case courtesy of Dr Ruslan Asadov (Picture courtesy: Radiopedia)	CT scan 10 mm in short-axis Loss of fatty hilum Focal necrosis Cystic necrotic nodes Long-to-short axis ratio (>2cm - usually benign)
Pneumomediastinum	Endoscopic procedures Intubation/extubation Central vascular access procedure Pleural cavity instrumentation Chest or abdominal surgery Direct chest wall trauma Tracheostomy Pulmonary barotrauma (scuba diver, free diver, airplane passenger)	Severe, acute pain in the chest (pain may radiate to the shoulders or back) Shortness of breath Fever Cervical pain (subcutaneous emphysema) Jaw pain (subcutaneous emphysema) Swelling of neck, face, chest, abdomen, shoulder (subcutaneous emphysema) Dysphonia Dysphagia Emesis	+	-	-	CT scan: Subcutaneous emphysema Naclerio V sign: Pneumomediastinum secondary to an esophageal rupture Pneumopericardium: Gas anterior to pericardium Ring around artery sign: Gas around pulmonary artery and main branches Tubular artery sign: Gas outlining major aortic branches Double bronchial wall sign: Gas outlining bronchial wall Continuous diaphragm sign: Gas trapped posterior to pericardium Extrapleural sign: Gas between parietal pleura and diaphragm Gas in pulmonary ligament Pediatric pneumomediastinum: Thymic wing sign: Elevated thymus Haystack sign (the heart appears like a haystack in a Monet painting)	CT scan shows extensipneumomediastiumium is demonstrated throughout the chest with no pneumothorax. Case courtesy of A.Prof Frank Gaillard Picture courtesy: Radiopedia)	Physical exam: Mediastinal crunch or click on auscultation over the cardiac apex and the left sternal border synchronous with the heart sound (Hamman's sign) Subcutaneous crepitation
Disease	Etiology	Symptoms	Dyspnea/ RI	Dysphagia	SVCS	Gold standard	Image	Additional findings
Sarcoidosis	African american race People of Scandinavian descent Exposure to dusty/moldy environments People between 25 and 40 years Genetic factors The first-degree relatives have 55 fold increased the risk HLA-DRB1*1101 is associated with cardiac sarcoidosis and hypercalcemia Lofgren's syndrome, HLA-DRB1*03 is 4 times higher BTNL-2 (butyrophilin-like 2) gene Immune system Higher expression of serum amyloid A Immune system exhaustion and failure of effective antigen clearence Drug side effect Adalimumab Etanercept Ipilimumab Infliximab	Cutaneous sarcoidosis Papular, nodular, plaque-like, lupus pernio, erythema nodosum, subcutaneous sarcoidosis Ocular sarcoidosis Dry eye, blurred vision, photophobia, red eye, pain Upper respiratory tract Cough Nasal congestion Nasal crusting Anosmia Epistaxis Nasal polyposis Cardiac sarcoidosis Palpitations Syncope Lightheadedness Chest pain Sudden cardiac death (SCD) Neurosarcoidosis Peripheral facial nerve palsy Polyuria - polydipsia Disturbance in body temperature and libido due to hypothalamic inflammation Seizures Impairment in sleep Reticuloendothelial system Neck or axillary mass Lymphadenopathy Hepatosplenomegaly Musculocutaneous Acute sarcoid arthritis or acute polyarthritis Chronic arthritis Myopathy(diffuse granulomatous myositis) Lofgren syndrome Erythema nodosum Hilar lymphadenopathy Migratory polyarthralgia Fever Exocrine glands Painless swelling of salivary glands and parotid gland Sicca syndrome and xerostomia Renal & electrolyte Renal colic caused by nephrolithiasis Uremia due to interstitial nephritis	+	-	-	Endoscopy with biopsy and histopathology Granulomas can be detected in any organ	CT scan shows extensive calcified lymph nodiiniin mediastinum, extensive architectural distortion of lung tissue, associated with marked fibrosis. Multiple pulmonary nodules are present in both lungs. Case courtesy of Prof Oliver Hennessy (Picture courtesy: Radiopedia)	Laboratory findings: Serum ACE levels greater than two times the upper limit of normal CT scan: Honeycombing Parenchymal nodules and opacities along bronchovascular bundles as well as in subpleural locations
Disease	Etiology	Symptoms	Dyspnea/ RI	Dysphagia	SVCS	Gold standard	Image	Additional findings
Infectious disease
Mediastinitis	Infection: Group A beta-hemolytic streptococci Streptococcus milleri Mycobacterium tuberculosis Histoplasma capsulatum Bacillus anthracis Candida albicans Risk factors: Recent chest surgery Endoscopy Obesity Smoking Immunodeficiency Intensive care unit stay > 2 days COPD Drug users Diabetes Kidney failure Peripheral vascular disease	Chest pain Cough Chills Fever Malaise Abdominal pain Hemoptysis Tachycardia	+	-	-	Culture and sensitivity of mediastinal tissue collected by biopsy/aspiration	CT scan shows airway narrowing of the right lower lobe bronchus. There is thickening of the right pleura and right interlobular septae. There are partially calcified right hilar and mediastinal lymph nodes. Case courtesy of Dr Darel E Heitkamp (Picture courtesy: Radiopedia)	Physical exam Chest wall tenderness Wound drainage Unstable chest wall CBC Leukocytosis CT scan Mediastinal or hilar mass Infiltrative region of soft-tissue attenuation which obliterates normal mediastinal fat planes and encases or invades adjacent structures Calcifications of the central mass or associated lymph nodes (especially if there has been preceding histoplasmosis) Tracheobronchial narrowing Pulmonary infiltrates
Anthrax	B. anthracis People at higher risk include Veterinarians Laboratory professionals dealing the bacteria Health care workers Livestock producers People who handle animal products Mail handlers, military personnel, and response workers, in case of bioterrorism People who make or play animal hide drums Travelers, particularly to the follow areas: Central and South America Sub-Saharan Africa Central and southwestern Asia Southern and eastern Europe The Caribbean	Inhalation or pulmonary anthrax Fatigue Body pain Fever and chills Sweating Headache Confusion or dizziness Sore throat Cough Chest discomfort Shortness of breath Nausea Vomiting Stomach pains	+	-	-	Culture and sensitivity: Serum Plasma Blood Pleural fluid CSF Biopsy specimen	CT scan shows showing bilateral pulmonary consolidation (yellow arrows) and pleural effusions (blue arrows). Case courtesy and picture courtesy: Centers for Disease Control and Prevention	CT scan Mediastinal widening Hyperdense lymph nodes in the mediastinum Lymph node hemorrhage and necrosis following spore germination and vegetative growth with exotoxin elaboration Edema of mediastinal fat PCR Confirms virulence of organism by virulence factor genes Primers to the toxin gene Primer for the enzyme of capsule formation gene
Tuberculosis	M. tuberculosis Traveling or living in endemic regions (Sub-saharan African, Russia, India, Pakistan, China) Elderly Infants IV drug users Immunosuppression: AIDS Diabetes Silicosis Malignancy, such as head and neck cancers Hematologic and reticuloendothelial disease End-stage kidney disease History of gastrectomy Malabsorption syndrome The risk of contracting TB increases in: Frequent contact with people who have TB Poor nutrition Smoking Bad hygiene	Cough (most common) Fever Night sweats Unexplained weight loss Hemoptysis Chest pain Anorexia Malaise Chills Fatigue	+	-	-	Culture and sensitivity	CT scan shows the cavity (arrows) and extensive endobronchial spread particularly within the left upper lobe (Circle). In places there is a tree-in-bud appearance. Case courtesy of DDrNatalie Yang (Picture courtesy: Radiopedia)	Chest X-ray Primary tuberculosis Parenchymal infiltrates Hiliar adenopathy Pleural effusion Tuberculomas (opacities similar to a lung mass) Unilateral pleural effusion may be observed Secondary Tuberculosis The most common location upper lobes, specially in the apical and posterior segment Patchy consolidation Cavitation, which is the most important finding in secondary tuberculosis Irregular margins and thick walls Seen in the upper lung Cavities may be superinfected An air-fluid level is seen Pneumothorax is rare Lymphadenopathy Small pleural effusion Consolidation involves more than one lobe
Disease	Etiology	Symptoms	Dyspnea/ RI	Dysphagia	SVCS	Gold standard	Image	Additional findings
Cystic mass
Bronchogenic cyst	Abnormal ventral budding or branching of the tracheobronchial tree during embryologic development	Pleuritic chest pain Cough Hemoptysis Fever Pneumonia secondary to airway obstruction	+	-	-	CT scan	CT scan shows a large fluid density cystic structure abutting the right side of the superior mediastinum without evidence of invasion into either the mediastinum or the lung. It is well circumscribed and has appearances most consistent with a bronchogenic cyst. Case courtesy of Dr Gagandeep Choudhary (Picture courtesy: Radiopedia)	CT scan: Spherical or oval mass Smooth outline Unilocular Noncalcified Demonstrating the size and shape of the cyst Determining its position in relation to other structures Bronchogenic cysts can mimic hydatid cysts Pneumonitis, pneumothorax, or empyema may present
Esophageal duplication cysts	Rare congenital gastrointestinal malformation	Chest pain Stridor Nonproductive cough Epigastric discomfort Vomiting Cardiac arrhythmia Retrosternal and thoracic back pain Cyst ulceration and bleeding Cyst rupture with secondary mediastinitis	-	+	-	Endoscopic ultrasound (EUS) Distinguish between solid and cystic lesions Periesophageal homogeneous-hypoechoic mass Multi-layered wall and well-defined margins Anechoic cyst if considerable central fluid present	CT scan shows in the posterior mediastinum, to the left of the esophagus and below the level of the carina is a low attenuation (20 HU), a non-enhancing mass which abuts and displaces the esophagus to the right side. Appearance and location are suggestive of foregut duplication cyst. Case courtesy of Dr Alexandra Stanislavsky (Picture courtesy: Radiopedia)	Endoscopic ultrasound-guided FNA Atypical in appearance for duplication cysts Malignancy suspicion Endoscopy Indistinguishable from a lipoma, leiomyoma, a gastrointestinal stromal tumor (GIST), or other submucosal lesions
Disease	Etiology	Symptoms	Dyspnea/ RI	Dysphagia	SVCS	Gold standard	Image	Additional findings
Lymphangioma	Turner syndrome Down syndrome Noonan syndrome Chronic lymphatic obstruction such as after surgery, infections or radiotherapy	Constipation Failure to thrive Signs and symptoms of genetic defects	+	+	-	Histopathology and cytology	CT scan shows cystic mass which was located on the posterior to the lower esophagus later diagnosed as thoracic duct lymphangioma. Source:Case courtesy of Jin San Bok et al, Department of Thoracic and Cardiovascular Surgery, Seoul National University Hospital	MRI: Degree of involvement and extent of lesion MRI can prevent extensive, incomplete surgical resection CT scan: Homogeneous, cystic mass Intrinsic septations Compression of adjacent organs
Chronic inflammatory disease
Churg-Strauss syndrome	HLA-DRB1*04 and *07 HLA - DRB4 Allergens Infections Vaccinations (eg, influenza) Drugs: Leukotriene receptor antagonists/ leukotriene modifying agents Anti IgE antibodies (eg, omalizumab) Mesalazine Propylthiouracil Methimazole Exposure to silica Cocaine	Chest tightness Cough Hemoptysis Asthma Weakness Malaise Fever Weight loss Arthralgia Fatigue	+	+/-	-	Lung biopsy 4 out of 6 positive : Asthma Eosinophilia Polyneuropathy or Mononeuropathy Non fixed pulmonary infiltrates Paranasal sinus that is abnormal Eosinophils that are extravascular	CT scan shows peripheral consolidation / ground glass opacity and solid centrilobular nodulesnon-cavitateded), except the left part which underwent slight changes with now a moderate pleural effusion. Case courtesy oDrDr Fabien Ho (Picture courtesy: Radiopedia)	High-resolution computerized tomography (HRCT): Airspace consolidations mostly bilateral and lobular Ground-glass opacities in a patchy or subpleural distribution Centrilobular nodules Bronchial wall thickening and/or dilatation Pleural effusions Hilar or mediastinal lymph node enlargement Interlobular septal thickening
Disease	Etiology	Symptoms	Dyspnea/ RI	Dysphagia	SVCS	Gold standard	Image	Additional findings
Posterior mediastinal mass
Cystic mass
Mediastinal neurenteric cyst	Developmental foregut anomaly	Neurologic impairment Back pain Gait disturbance Sensory deficit Motor deficit Stridor Persistent cough	+	+/-	-	CT scan: Cystic nature of the mass Extent of the mass Vertebral anomalies	CT showing a well-defined posterior mediastinal cystic lesion (highlight) is seen with air-fluid levels showing mucosal enhancement. A cystic mass is extending in between and is displacing descending thoracic aorta anteriorly (curved arrow), azygous vein posteriorly (straight arrow). Source: Case courtesy of Taruna Yadav et al	Postnatal chest X-ray: Posterior mediastinal mass with associated vertebral anomalies Ultrasound: Cystic nature of the mass
Pancreatic pseudocyst	Acute pancreatitis Chronic pancreatitis	Abdominal pain - constant pain or deep ache in the abdomen Pain radiating to the back Abdominal mass Bloating of the abdomen Difficulty eating Indigestion	-	-	-	Histopathology and cytology of cyst and fluid content	CT scan showing a low attenuating thick walled peripherally enhancing cystic lesion, measuring approximately 5.2 x 2.8 cm noted in the lower aspect of posterior mediastinum and appears to arise adjacent to the esophageal hiatus and extending up to the carina. Case courtesy of Dr Prashant Mudgal (Picture courtesy:Radiopedia)	CT scan Thin-walled Fluid-containing cyst within the posterior mediastinum In continuity with the intrapancreatic or peripancreatic fluid collections
Disease	Etiology	Symptoms	Dyspnea/ RI	Dysphagia	SVCS	Gold standard	Image	Additional findings
Central nervous system disease
Meningocele	Maternal nutritional factors Alcohol use Caffeine use Low folate intake Elevated glycemic load or index Low methionine intake Low serum choline level Low serum vitamin B12 level Low vitamin C level Low zinc intake Smoking Hyperthermia Maternal infections and illnesses Pregestational insulin-dependent diabetes Pregestational obesity Psychosocial stress Valproic acid use Environmental factors Ambient air pollution Disinfectant by-products in drinking water Indoor air pollution Nitrate-related compounds Organic solvents Pesticides Polycyclic aromatic hydrocarbons	Symptoms depend on the severity of the defect Weakness or paralysis in the legs Urinary incontinence Bowel incontinence Sensation problems in the lower extremity Motor problems in the lower extremity Headache Orthopedic abnormalities: Club foot Hip dislocation Scoliosis Difficulties with executive functions including: Planning Organizing Initiating Memory Abstraction Attention problems	-	-	-	Prenatal 2D/3D ultrasound: Vertebral defect Splayed vertebral pedicles Disrupted vertebrae Postnatal MRI	CT scan showing Right thoracic CSF cyst with smaller left sided out-pouching. Case courtesy of Dr G Balachandran (Picture courtesy: Radiopedia)	Laboratory tests: Elevated maternal serum alpha-fetoprotein MRI: Herniation of a CSF filled sac through spina bifida CSF attenuation lesion in conus medullaris and other parts of the CNS Short and thick filum terminale
Neurilemmoma (Spinal schwannoma)	Neurofibromatosis type II Schwannomatosis Carney complex	Sharp, aching, or burning pain Pins-and-needles sensation Muscle weakness Numbness Nighttime pain in back or neck	-	-	-	Biopsy with histopathology	CT scan showing a soft tissue density lesion within the left posterior mediastinum, in a paravertebral location. The lesion is closely related to the left neural exit foramen, but there is no definite extension into the spinal canal. The lesion does extend into the intercostal space. Case courtesy of Dr Paul Leong (Picture courtesy:Radiopedia)	MRI Tumor outside of a nerve or part of a nerve and if it involves other nearby structures
ABBREVIATIONS: N/A: Not available, SOB: Shortness of breath, M/C: Most common, RI: Respiratory insufficiency, NM: Neuromuscular system, SVCS: Superior vena cava syndrome, SLE: Systemic lupus erythematosus disease, T3: Triiodothyronine, T4: Thyroxine, TSH: Thyroid stimulating hormone, TFT: Thyroid function test, MRI: Magnetic resonance imaging, CNS: Central nervous system, CSF: Cerebrospinal fluid, FNA: Fine needle aspiration, CBC: Complete blood count, COPD: Chronic obstructive pulmonary disease, AIDS: Acquired immune deficiency syndrome, HIV: Human immunodeficiency virus, Hep C: Hepatitis C virus, HTLV-1: human T-lymphotropic virus, EBV: Epstein Barr virus, HHV-8: Human herpes virus-8