Unilateral Mediastinal Mass



Unilateral Mediastinal Mass


Toms Franquet, MD, PhD



DIFFERENTIAL DIAGNOSIS


Common



  • Thyroid Goiter


  • Thymoma


  • Teratoma


  • Lymphoma


  • Pericardial Cyst


  • Bronchogenic Cyst


  • Neurogenic Tumors


  • Pleuropericardial Fat Pad


  • Aortic Aneurysm


Less Common



  • Thymic Carcinoma


  • Thymic Cyst


  • Lymphangioma


  • Malignant Germ Cell Tumors


  • Esophageal Duplication Cyst


Rare but Important



  • Parathyroid Adenoma


  • Thymolipoma


  • Hemangioma


  • Meningocele


  • Thoracic Duct Cyst


  • Gastroenteric (Neurenteric) Cyst


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Chest radiograph is of limited value in differential diagnosis of mediastinal masses


  • Combination of location of mass, demographics, and imaging (CT, MR) may allow confident diagnosis


  • Clinical history is key in diagnosing lymphoma, extramedullary hematopoiesis, thymoma (myasthenia gravis), thymic carcinoid (hormone syndrome, e.g., Cushing or MEN)


Helpful Clues for Common Diagnoses



  • Thyroid Goiter



    • Most commonly in women


    • Right-sided mediastinal mass with contralateral tracheal displacement


    • High attenuation value (> 100 HU) on NECT


  • Thymoma



    • Well-defined, round or ovoid, anterior mediastinal mass


    • Variable size


    • Homogeneous or heterogeneous


    • Areas of hemorrhage, necrosis, or cyst formation (CT, MR)


    • Punctate, linear, or ring-like calcification (CT)


    • May result in pleural dissemination (“drop metastases”)


  • Teratoma



    • In anterior mediastinum (> 80%)


    • Adipose tissue component is common (> 80%)


    • Heterogeneous appearance on CT and MR


    • CT and MR useful to identify small foci of fat


  • Lymphoma



    • Non-Hodgkin lymphoma



      • Most frequent lymphoma (> 75%)


      • Large B-cell lymphoma: Young adults (20s and 30s), female predominance


    • Hodgkin lymphoma (nodular sclerosis)



      • Bulky anterior mass (40%)


      • Young adults (20s and 30s)


  • Pericardial Cyst



    • Usually in cardiophrenic angle


  • Bronchogenic Cyst



    • Variable origin: Paratracheal, carinal, hilar, paraesophageal, and extramediastinal


    • CT: 50% have high attenuation value (> 130 HU); wall calcification in 10%; rarely, milk of calcium in cyst fluid


  • Neurogenic Tumors



    • Neurofibroma



      • Paravertebral region or along nerve


      • Low attenuation value (20-25 HU) on NECT


    • Neurilemoma (schwannoma)



      • Paravertebral region or along nerve


      • Adjacent bone changes may be present (50%)


    • Ganglioneuroma



      • Predominantly in infants and children; 60% in patients < 20 years old


      • Low attenuation value on NECT


    • Ganglioneuroblastoma



      • Rare after age 10; oval lesions oriented in vertical axis (sympathetic chain)


      • Variable appearance: Homogeneous solid to cystic masses


    • Paraganglioma



      • Near base of heart and great vessels (adjacent to pericardium)



    • Usually bilateral; may be asymmetrical


  • Aortic Aneurysm



    • Consider aneurysm of any mass contiguous with any part of aorta


Helpful Clues for Less Common Diagnoses



  • Thymic Carcinoma



    • Most common histologic subtypes: Squamous cell carcinoma and neuroendocrine carcinoma


    • CT and MR: Irregular contour, necrotic or cystic component, heterogeneous contrast enhancement, great vessel invasion


    • Higher maximal standardized uptake values and homogeneous FDG uptake than thymoma


  • Thymic Cyst



    • Congenital



      • Unilocular; homogeneous water density (0-20 HU) on NECT


      • Wall imperceptible on CT


    • Acquired



      • Multilocular; higher attenuation than water


      • Evident cyst wall on CT


  • Lymphangioma



    • Usually found in neck or axilla; anterior mediastinum (10%); unilocular or multilocular (30%)


    • May insinuate around normal structures


  • Esophageal Duplication Cyst



    • Sharply marginated masses in middle or posterior mediastinum


    • CT: Round or tubular water attenuation masses near or within (intramural) esophageal wall


Helpful Clues for Rare Diagnoses



  • Parathyroid Adenoma



    • Most are very small; appearance similar to that of a lymph node


    • Optimal assessment by Tc-99m sestamibi combined with SPECT


  • Thymolipoma



    • Entirely asymptomatic


    • May mimic cardiomegaly


    • Positional changes in shape (soft consistency)


  • Hemangioma



    • Most are asymptomatic


    • Phleboliths visible (10%)


    • Heterogeneous appearance in both NECT and CECT


  • Meningocele



    • Classic location: Between thoracic inlet and diaphragm


    • Continuity between CSF in thecal sac and meningocele typical


  • Thoracic Duct Cyst



    • Small round or oval cystic mass in posterior mediastinum


  • Gastroenteric (Neurenteric) Cyst



    • Diagnosis: Childhood


    • Round or lobulated mass; homogeneously dense


    • Neurenteric: When it is associated with spinal column anomalies (symptomatic)






Image Gallery









Frontal radiograph shows a large mass in the superior mediastinum image displacing the trachea laterally image.






Axial NECT shows a large, homogeneous, middle mediastinal mass displacing the bronchi anteriorly with resulting airway compression image.

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Aug 8, 2016 | Posted by in CARDIOLOGY | Comments Off on Unilateral Mediastinal Mass

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