Mediastinal Masses

Malignant and Benign Lesions

• • 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

Neurogenic Tumors

• • 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

Mediastinal Cystic Lesions

• • 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

Germ Cell Tumors

• • 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

Lymphomas

• • Usually disseminated disease

  • Anterior compartment most common but can be anywhere in mediastinum

  • Second most common mass in anterior mediastinum

Epidemiology

• • 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

Symptoms and Signs

• • 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

Laboratory Findings

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

Imaging Findings

• • Chest film: Demonstrates mass

  • Chest CT:...