Contrast-Enhancing Mass, Mediastinum or Hilum
Jud W. Gurney, MD, FACR
DIFFERENTIAL DIAGNOSIS
Common
Aneurysm
Goiter
Less Common
Varices
Tuberculosis
Castleman Disease
Parathyroid Adenoma
Acute Mediastinitis
Kaposi Sarcoma
Hemangioma
Metastases
Thymic Carcinoid
Rare but Important
Paraganglioma
Extramedullary Hematopoiesis
Bacillary Angiomatosis
Kimura Disease
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
Mnemonic: ATTACK PAIN
Aneurysm, Thyroid (goiter), Tuberculosis, Angiofollicular hyperplasia (Castleman), Carcinoid (thymic), Kaposi sarcoma
Parathyroid Adenoma, Infection (mediastinitis), Neuroendocrine (paraganglioma)
Helpful Clues for Common Diagnoses
Aneurysm
Due to atherosclerosis, trauma, mycotic infection, cystic medial necrosis, vasculitis
Wall may have curvilinear calcification
Consider perforation in patients with left pleural effusion
Any mediastinal mass should be considered as possible aneurysm
Goiter
Develop in 5% worldwide
Up to 20% descend into mediastinum
NECT: High attenuation due to natural iodine; 70-120 HU
May also have calcifications (coarse, punctate, or rings)
Anterior to trachea (75%), usually left side predominant
Posterior to trachea (25%), usually right side predominant
Helpful Clues for Less Common Diagnoses
Varices
From portal hypertension, flow through left gastric vein to esophageal venous plexus
Dilated serpiginous veins in azygoesophageal recess, may be unopacified on arterial phase imaging
CT findings include cirrhotic contour liver and splenomegaly
Tuberculosis
Enlarged rim-enhanced lymph nodes
Low-attenuation center represents caseous necrosis
Indicates active disease, typically primary disease
Castleman Disease
Angiofollicular lymph node hyperplasia
Histology: Hyaline vascular (90%), plasma cell (10%)
Localized: Hyaline vascular (90%) and asymptomatic
Multicentric: Plasma cell (80%) and often symptomatic
70% occurs in thorax
Avid, uniform contrast enhancement is characteristic, especially in hyaline vascular type
Parathyroid Adenoma
10% ectopic (50% in anterior mediastinum usually near thymus)
Less common in paraesophageal region or aortopulmonary window
Benign tumor that results in hyperparathyroidism
Tumors usually < 3 cm diameter
25% demonstrate mild enhancement
Acute Mediastinitis
Most associated with median sternotomy or esophageal perforation
Less commonly descend from retropharyngeal infection
CT findings include effacement of normal mediastinal fat, fluid collections, extraluminal gas
Kaposi Sarcoma
Imaging appearance overlaps with multicentric Castleman disease
Hemangioma
< 1% of mediastinal masses
Most common in superior or anterior mediastinum
Phleboliths (10-40%)
Intralesional fat also common (40%)
Heterogeneous contrast enhancement: 4 patterns
Central (60%), peripheral (10%), central and peripheral (20%), nonspecific (10%)
Metastases
Vascular tumors: Renal cell carcinoma, papillary thyroid, small cell carcinoma, melanoma
Metastases to mediastinum from extrathoracic tumors uncommon
Genitourinary tumors: Renal cell, transitional cell, prostate, uterine, ovarian, testicular
Head & neck tumors: Squamous cell, thyroid
Breast
Melanoma
Thymic Carcinoid
Large size is common, averaging 10-12 cm
May have metastases to lung, brain, lymph nodes, and pleura
Osseous metastasis often osteoblastic
1/3 have paraneoplastic syndrome, usually Cushing syndrome
Curiously, carcinoid syndrome has not been reported
20% associated with type 1 MEN syndrome
Helpful Clues for Rare Diagnoses
Paraganglioma
Most are asymptomatic
Enhancement often intense
Most located in posterior mediastinum
Aortopulmonary recess, subcarinal or pericardiac region well-described locations
Extramedullary Hematopoiesis
Posterior mediastinal masses usually caudal to 6th thoracic vertebra
May contain fat
Centered on vertebral body
Ribs usually demonstrate marrow expansion
Bacillary Angiomatosis
Caused by Bartonella henselae or B. quintana
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