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Malignant and Benign Lesions

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  • • Divided into 3 regions

    • -Anterior

      -Middle (great vessels, heart, trachea, and esophagus)

      -Posterior

    • Neurogenic tumors most common masses in children (50-60%);

    • -In children younger than 4 years, masses are invariably malignant (neuroblastomas)

    • Neurogenic tumors most common mediastinal mass in adults

    • -Posterior compartment typical

      -Well circumscribed, calcified, benign

    • Anterior masses:

    • -More often malignant than neurogenic tumors

      -Thymoma most common then lymphoma

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Neurogenic Tumors

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  • • Posterior mediastinum, often superiorly from intercostal or sympathetic nerves

    • Nerve sheath tumors (eg, schwannoma and neurofibroma) most common (40-65%)

    • Usually benign, 10% malignant

    • Malignant tumors arise from nerve cells (neuroblastoma); more common in children

    • May be multiple or dumbbell shape

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Mediastinal Cystic Lesions

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  • • Arise from pericardium, bronchi, esophagus, or thymus

    • 75% located near cardiophrenic angles, 75% on right side

    • 10% are diverticula of pericardial sac that communicate with pericardial space

    • Bronchogenic cysts arise below carina

    • Enterogenous cysts arise along esophagus, may be incorporated, and associated with vertebral anomalies

    • 10% nonspecific without identifiable lining

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Germ Cell Tumors

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  • • Common in anterior mediastinum

    • Both solid and cystic, may contain teeth or hair

    • Ectodermal, endodermal, mesodermal elements present

    • Most metastatic from retroperitoneal disease; < 5% are primary tumors

    • Seminoma (40%), embryonal carcinomas and nongestational choriocarcinomas (20%), yolk sac (20%), and teratomas (20%) can have both benign and malignant components

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Lymphomas

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  • • Usually disseminated disease

    • Anterior compartment most common but can be anywhere in mediastinum

    • Second most common mass in anterior mediastinum

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Epidemiology

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  • • Mediastinal masses account for < 20% of all thoracic tumors

    • Most masses in adults are benign, with recent shift toward more malignant tumors

    • Prevalence: Substernal goiter is most common, then neurogenic tumors (26%), cysts (21%), teratodermoids (16%), thymomas (12%), lymphomas (12%)

    • 25% of masses are malignant

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Symptoms and Signs

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  • • Symptoms more common in malignant lesions

    • 50% of patients have cough, wheezing, dyspnea, or recurrent pneumonias

    • Hemoptysis, chest pain, weight loss, and dysphagia less common, each occurring in 10% of patients

    • Myasthenia, fever, superior vena cava (SVC) obstruction, each occurring in 5%

    • Cancer suggested if following symptoms are present:

    • -Hoarseness

      -Horner syndrome

      -Severe pain

      -SVC obstruction

      -Chylothorax (lymphoma)

    • Fever in Hodgkin disease

    Thymoma: Myasthenia (15-20%), hypogammaglobulinemia, Whipple disease, red blood cell aplasia, Cushing disease

    Hypoglycemia: Rarely in mesothelioma, teratoma, fibroma

    • Hypertension and diarrhea in pheochromocytoma and ganglioneuroma

    • Neurologic deficits from neurogenic tumors

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Laboratory Findings

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  • • > 90% of germ cell tumors produce βhCG, alpha-fetoprotein (AFP), lactic dehydrogenase (LDH)

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Imaging Findings

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  • Chest film: Demonstrates mass

    Chest CT: Diagnostic test of choice

    MRI

    • -Useful to assess vascular or spinal cord extension

      -In neurogenic tumors, determines intraspinal extension

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