Masses of the Middle Mediastinum




TERMINOLOGY





  • Amyloidosis



  • Angioimmunoblastic lymphadenopathy



  • Angiomatous lymphoid hamartomas



  • Azygos vein varix



  • Benign mediastinal lymphadenopathy



  • Bronchogenic cyst



  • Castleman’s disease



  • Chylous cysts



  • Clear water cyst



  • Congenital hernia



  • Cystic hygroma



  • Diaphragmatic hernias



  • Enterogenous cysts



  • Esophageal duplication cyst



  • Foregut cysts



  • Germ cell tumors



  • Hemangioma



  • Hiatal hernia



  • Hodgkin’s disease (HD)



  • Human herpes virus 8



  • Kaposi sarcoma–associated herpesvirus



  • Kaposi’s sarcoma



  • Large B cell lymphoma



  • Lymphangioma



  • Lymphatic cysts



  • Lymphoblastic lymphoma



  • Lymphoma



  • Malignant hemangiopericytoma



  • Metastatic mediastinal lymphadenopathy



  • Middle mediastinal mass



  • Neurenteric cyst



  • Non-Hodgkin’s lymphoma (NHL)



  • Pancreatic pseudocyst



  • Paraganglioma



  • Pericardial cyst



  • POEMS syndrome



  • Reed-Sternberg cells



  • Spring water cyst



  • Vascular aneurysm



  • Vascular hamartoma





ANATOMY


The middle mediastinum contains the heart, pericardium, aortic arch and great vessels, trachea, bronchi, upper esophagus, and lymph nodes ( Fig. 43-1 ).




Figure 43-1


Figure depicting anatomic subdivision of the middle mediastinum.

(From Townsend CM, Beauchamp RD, Evers BM, Mattos KL, editors. Sabiston textbook of general surgery. 17th ed. New York: Elsevier; 2004.)




INTRODUCTION


The majority of the patients with mediastinal masses do not demonstrate clinical symptoms, and the masses are found incidentally on chest radiograph. However, some patients exhibit generalized and nonspecific symptoms due to localized compression or invasion of surrounding structures. The masses localized in the middle mediastinum pose a diagnostic challenge because of its relatively inaccessible site with routine clinical testing. Even though the majority of the mediastinal masses are benign (67%), most patients require further diagnostic testing to establish tissue diagnosis. Patient’s age, clinical symptoms, and location of the mass determine the likelihood of malignancy.




SYMPTOMS


Symptoms are related to local compression or invasion of surrounding tissues. Localizing clinical symptoms include cough (60%), chest pain (30%), and dyspnea (16%).




SPECIFIC MASSES OF THE MIDDLE MEDIASTINUM: CYSTS





  • Foregut cysts




    • Ten to twenty percent of mediastinal masses



    • Twenty percent cannot be classified (indeterminate cysts or nonspecific)



    • Derived from embryonic developmental abnormality



    • Composed of bronchogenic and enterogenous cysts



    • Equal predilection in both sexes except for slightly higher male predominance in neurenteric cysts




  • Bronchogenic cysts




    • Pathogenesis




      • Derived from abnormal budding of the ventral foregut during development



      • Respiratory columnar epithelial lining



      • Cysts migrate to atypical locations



      • Arise adjacent to trachea, main bronchi, and carina (85%)



      • Occur in the lung (15%)



      • Located mainly in the middle and posterior mediastinum



      • Other sites include pleura, diaphragm, pericardium, and neck.



      • Cysts contain fluid, mucus, milk of calcium, blood, or purulent material



      • Represents 50% to 60% of mediastinal cysts




    • Demographics




      • Commonly affects adult patients (average age 36)



      • Most common form of foregut cysts




    • Symptoms/findings




      • Forty to sixty-seven percent with symptoms



      • Cough, wheezing, dyspnea, dysphagia, chest pain, or hemoptysis



      • Large cysts may compress airways resulting in airway obstruction



      • Other serious complications include superior vena cava obstruction, extrinsic pulmonary artery stenosis, pericardial tamponade, and severe hemoptysis




    • Radiographic findings ( Fig. 43-2 )




      • Well-circumscribed, spherical, mediastinal mass



      • Chest computed tomography (CT) scan shows homogenous, nonenhancing mass with variable attenuation.



      • Cyst wall contains calcification or enhancement.



      • Extension to tracheobronchial tree results in cyst with air-fluid level, air trapping, atelectasis, and tracheal deviation.



      • Associated with cartilage in cyst






      Figure 43-2


      Bronchogenic cyst depicted in chest radiograph ( A ) and chest CT ( B ).



    • Diagnosis




      • Surgical excision



      • Thorascopic or bronchoscopic needle aspiration of nonhemorrhagic fluid with mucus and bronchial cells (poor specificity)




    • Treatment




      • Symptomatic patients require definitive surgical resection



      • Some asymptomatic patients may require complete surgical excision to establish diagnosis and to prevent complication



      • Bronchoscopic or thorascopic needle aspiration for patients with high surgical risk



      • Risk of recurrence with needle aspiration





  • Enterogenous cysts




    • Classification




      • Esophageal duplication cyst



      • Neurenteric cyst



      • Accounts for 5% to 10% of cysts




    • Pathogenesis




      • Originate from dorsal foregut



      • Located in middle or posterior mediastinum



      • Cysts contain gastric mucosa, pancreatic tissue, or neural tissue.



      • Esophageal duplication cyst




        • Develops from persistent diverticulum of the dorsal bud of the foregut during early development



        • Manifests as paraesophageal tubular lesions



        • Migrates with the lung bud during development and may be located distant from the esophagus




      • Neurenteric cyst




        • Forms when the foregut and notochord fail to separate



        • Contains enteric and neural tissue



        • Associated with vertebral anomalies (50%) including scoliosis, anterior spina bifida, vertebral fusion, hemivertebra, and butterfly vertebrae



        • Attachment and intraspinal extension to the spine (20%)





    • Demographics




      • Discovered during childhood due to tracheobronchial or esophageal compression



      • Seventy-five percent of esophageal duplication cyst are discovered by age 1 year owing to acid secretion causing localized symptoms




    • Symptoms/findings




      • Mostly asymptomatic but risk of hemorrhage or rupture



      • Esophageal duplication cyst




        • Associated with congenital gastrointestinal (GI) tract malformations (12%)




      • Neurenteric cyst




        • Neurologic symptoms due to intraspinal involvement





    • Radiographic findings




      • Similar radiographic pattern as bronchogenic cysts



      • Rarely see cysts with calcification



      • Esophageal duplication cyst




        • Adjacent or located within wall of esophagus



        • Usually located right side of the esophagus



        • Barium esophagram may show extrinsic compression of the esophagus by the cyst




      • Neurenteric cyst




        • Located mainly in the posterior mediastinum (90%)



        • Magnetic resonance imaging (MRI) scan required to exclude intraspinal extension





    • Diagnosis




      • Surgical biopsy



      • Classified by histologic features rather than location



      • Enterogenous cysts develop structures of GI tract




    • Treatment




      • Surgical excision via video-assisted thoracic surgery



      • Neurenteric cyst excision with excellent prognosis



      • Asymptomatic patients may require complete surgical excision to establish diagnosis and to prevent complication





  • Pericardial cysts




    • Pathogenesis




      • Develop from abnormal fusion of the anterior pericardial recesses



      • Attach to diaphragm or anterior pericardium



      • Rarely communicates with the pericardial sac



      • Spring water cysts or clear water cysts




    • Demographics




      • Occurs in 1 in 100,000 patients



      • Discovered during fourth to fifth decades of life




    • Symptom/findings




      • Mostly asymptomatic



      • Chest pain, cough, or dyspnea




    • Radiographic findings ( Fig. 43-3 )




      • Well-circumscribed, spherical or teardrop-shaped mass



      • Adjacent to the anterior chest wall, diaphragm, and heart



      • With or without calcification within wall of the cyst



      • CT scan of the chest shows nonenhancing, unilocular cystic mass with water attenuation.



      • Located in the right costophrenic angle (70%), left costophrenic angle (22%), and other paracardiac location (8%)










      Figure 43-3


      Pericardial cyst. On plain chest radiograph ( A ) obscuration of the right-sided heart border is evident. On CT ( B ) and MR ( C and D ), the cyst is clearly defined.



    • Diagnosis




      • Radiographic and clinical diagnosis




    • Treatment




      • Percutaneous aspiration of cyst for diagnosis before resection



      • Surgical resection with clinical symptoms



      • Follow clinically and radiologically for asymptomatic patients







VASCULAR MASSES





  • Key points




    • Ten percent of mediastinal masses



    • Occur in all compartments of mediastinum



    • Obtain CT scan of the chest with contrast, MRI, or angiography



    • Appearance is similar to neoplasm on chest radiograph




  • Paragangliomas




    • Pathogenesis




      • Slow-growing tumors



      • Hypervascular



      • Locally invasive



      • Recurrence rate 55%



      • Metastases 26%



      • Seventy-nine total cases involving anterior and middle mediastinum




    • Symptoms/findings




      • Often asymptomatic



      • Locally compressive symptoms




    • Radiographic findings




      • Enhancing mass




    • Diagnosis




      • Tissue diagnosis



      • Angiographic study reveals feeding vessels from bronchial arteries




    • Treatment




      • Preoperative embolization to minimize vascular complications



      • Surgical resection



      • Complete resection difficult given proximity to great vessels, heart, and trachea



      • High local recurrence rate



      • Not responsive to chemotherapy or radiation





  • Malignant hemangiopericytoma




    • Pathogenesis




      • Malignant spindle cell cancer



      • Vascular tumor arise from capillaries



      • Arranged in islands separated by thin walled vessels



      • Found in any part of the body



        • 1.

          Demographics




      • No sex predilection



      • Any age group




    • Symptoms/findings




      • Most asymptomatic



      • Symptoms related to local compression or metastasis




    • Radiographic findings




      • Well-circumscribed mass




    • Diagnosis




      • Tissue diagnosis




    • Treatment




      • Wide local surgical excision



      • Adjuvant radiation therapy





  • Hemangiomas




    • Classification




      • Alveolar capillary endothelial cell type



      • Pericytes of Zimmermann type




    • Pathogenesis




      • Derived from capillary endothelium



      • Other types include hemangioblastomas, vascular endotheliomas, capillary hemangiomas, capillary cavernous hemangiomas, and sclerosing hemangiomas




    • Demographics




      • Women older than 30 years of age




    • Symptoms/findings




      • Hemoptysis




    • Radiographic findings



    • Diagnosis




      • Tissue diagnosis




    • Treatment




      • Surgical resection with lobectomy of the lung





  • Systemic venous system




    • Superior vena cava



    • Azygos vein




      • Giant venous varix of the azygos arch



      • Etiologies include superior vena cava syndrome, Budd-Chiari syndrome, hypervascular tumor, pregnancy, post-traumatic pseudoaneurysm, kinking of the aorta, and portal vein hypertension from liver cirrhosis.



      • Mimics posterior mediastinal mass



      • CT of the chest with intravenous contrast recommended to delineate structures



      • Change in size of mass with position on chest radiograph



      • Mediastinoscopy or percutaneous fine-needle aspiration is contraindicated




    • Hemiazygos



    • Innominate veins



    • Located in the middle or superior mediastinum




  • Pulmonary arterial system




    • Pulmonary trunk abnormality



    • Main pulmonary artery abnormality



    • Middle mediastinal or perihilar masses




  • Pulmonary venous system




    • Partial anomalous pulmonary venous return



    • Pulmonary vein varix



    • Masses in the middle or superior mediastinum




  • Systemic arterial system




    • Innominate arterial aneurysm




      • Appear as curvilinear density above the right clavicle



        • 1.

          Aberrant right sublclavian artery




      • Originate from left sided aortic arch



      • Common congenital abnormality of the aortic arch



      • Dysphagia lusoria



      • Barium esophagram demonstrates anterior displacement of the posterior wall of the esophagus at the level of the aortic arch.



      • Aortogram, CT scan, and MRI are diagnostic.




    • Thoracic aortic aneurysm




      • Elderly patients with arteriosclerosis and hypertension



      • Trauma



      • Syphilis



      • Cystic medial necrosis



      • Peripheral calcification



      • Intrinsic pulsations on fluoroscopy



      • Angiogram for diagnosis



      • MRI scan to evaluate aorta and branching vessels





  • Vascular hamartoma, lymphatic type (cystic lymphangiomas)



  • See below in lymph node enlargement section under lymphangioma





LYMPH NODE ENLARGEMENT





  • Lymphoma




    • Primary mediastinal lymphoma (10%)



    • Usually occurs in anterior mediastinum but may involve middle mediastinum



    • Composed of Hodgkin’s disease (HD) and non-Hodgkin’s lymphoma (NHD)




  • HD




    • Pathogenesis




      • Large inflammatory cell reaction within fibrotic stroma



      • Enlarged nodes that may undergo necrosis or hemorrhage



      • Produce epithelial-lined cystic areas in the thymus




    • Demographics




      • Fifty percent with mediastinal involvement



      • Bimodal age distribution during early adulthood and age older than 50 years



      • Younger patients (age 29) with mediastinal involvement



      • Both sexes equally affected except for nodular sclerosing HD, which occurs two times more in women.



      • Most common mediastinal lymphoma.




    • Types of HD




      • Nodular sclerosing (66%): mostly affects anterior mediastinum including the thymus



      • Mixed cellularity (25%)



      • Lymphocyte depleted (5%)



      • Diffuse lymphocyte predominant (<3%)



      • Nodular lymphocyte predominant (<3%)




    • Symptoms/findings




      • Constitutional symptoms including fevers, night sweats, and weight loss (20%–30%)



      • Cough, dyspnea, wheezing, chest pain, and dysphagia



      • Pleural effusions, superior vena cava syndrome, and chest wall invasion



      • Cervical or supraclavicular lymphadenopathy




    • Radiographic findings


Jun 24, 2019 | Posted by in CARDIAC SURGERY | Comments Off on Masses of the Middle Mediastinum
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