Mediastinal mass

A mediastinal mass is an abnormal growth or lesion located within the mediastinum that can manifest at any age. Causes may be benign or malignant and include thymomas, lymphomas, neurogenic tumors, germ cell tumors, thyroid masses, benign cysts, and metastatic cancer. Clinical features depend on the location and size of the mass, ranging from asymptomatic to compressive effects such as dyspnea, chest pain, and superior vena cava syndrome. Diagnosis involves imaging, particularly contrast-enhanced CT or MRI, and, in some cases, cause-specific laboratory studies (e.g., tumor markers) and/or biopsy. Management varies by cause and may include observation for benign lesions; surgical resection and systemic treatment such as chemotherapy or radiation therapy for malignancies; and symptomatic treatment. Early multidisciplinary involvement is critical to optimize outcomes.

• Most common in adults: thymic tumors, thyroid masses, lymphomas ^[1]
• Most common in children: lymphomas, neurogenic tumors, germ cell tumors, benign mediastinal cysts ^[1]

Epidemiological data refers to the US, unless otherwise specified.

Causes vary based on the affected compartments of the mediastinum. ^[2][3]

Anterior mediastinum ^[1][2][4]

• Thymic tumors
  • Thymoma
  • Thymic carcinoma
  • Thymic carcinoids
• Thymic hyperplasia
• Thymic cysts
• Substernal goiter
• Lymphomas
  • Hodgkin lymphoma
  • Non-Hodgkin lymphoma
• Germ cell tumors (e.g., benign teratoma, nonseminomatous germ cell tumor, seminoma)
• Lipomas
• Abscesses

Middle mediastinum ^[2][4]

• Benign mediastinal cysts (e.g., bronchogenic cyst, esophageal duplication cyst, pericardial cyst)
• Esophageal disorders (e.g., esophageal cancer)
• Bilateral hilar lymphadenopathy (e.g., due to lymphoma, sarcoidosis, lung cancer metastases)
• Vascular masses (e.g., aneurysm)
• Abscesses

Posterior mediastinum ^[2][4]

• Neurogenic tumors (e.g., neuroendocrine tumor, schwannoma, neurofibroma)
• Meningoceles
• Spinal lesions (e.g., due to multiple myeloma, diskitis, osteomyelitis)
• Liposarcomas

Neurogenic tumors are the most common posterior mediastinal mass.

Focused history ^[1][4]

• Systemic symptoms (e.g., fever, night sweats, weight loss)
• Features of paraneoplastic syndromes (e.g., weakness in patients with a thymoma who have myasthenia gravis) ^[1]
• Localizing symptoms (e.g., chest pain, cough, dyspnea, hoarseness, dysphagia, focal weakness)
• History of previous malignancy, autoimmune disease, or infection
• Family history of malignancy or genetic condition associated with mediastinal masses

Focused examination ^[1][4]

• Assess for signs of local compression, e.g.:
  • Signs of respiratory distress (e.g., stridor, wheeze)
  • Signs of superior vena cava syndrome (e.g., facial swelling, cyanosis, distended neck veins)
  • Signs of nerve compression (e.g., limb, diaphragm, or vocal cord paralysis, Horner syndrome)
• Assess for signs of specific causes, e.g.:
  • Systemic illness (e.g., fever, cachexia, lymphadenopathy)
  • Thyroid disease (e.g., thyroid mass or enlargement)
  • Autoimmune disease (e.g., rash, arthralgia)

General principles ^[1][3]

• A mediastinal mass may be an incidental imaging finding.
• Obtain cross-sectional imaging to confirm the diagnosis in patients with a suspected mediastinal mass on clinical evaluation.
• Consider additional testing guided by the suspected underlying cause.

Imaging ^[3][4]

• Chest x-ray
  • Often the initial study performed
  • Possible findings
    • Loss of normal mediastinal border (silhouette sign)
    • Abnormal thickening of the anterior junction line ^[3]
• Cross-sectional imaging
  • CT chest with IV contrast: study of choice ^[3]
  • MRI chest: preferred in certain cases (e.g., to evaluate suspected cystic lesions or to differentiate between thymic hyperplasia and thymoma)
  • See “Common causes of mediastinal masses” for specific findings.

Additional testing

• Laboratory studies
  • Thyroid function tests if an endocrine disorder is suspected
  • Serum autoantibodies if myasthenia gravis is suspected
  • Tumor markers (e.g., alpha-fetoprotein, β-hCG) if a germ cell tumor is suspected
• Biopsy: usually reserved for suspected malignancies or if imaging is inconclusive

Approach ^[5][6]

Asymptomatic patients (incidental finding)

• See “Diagnostics.”
• Manage the identified underlying cause.

Symptomatic patients

• Screen for red flags in mediastinal masses and, if present:
  • Perform ABCDE survey, including:
    • Respiratory support for mediastinal masses
    • Hemodynamic support for mediastinal masses
  • Consult anesthesia, thoracic surgery, and critical care urgently for patients at risk of respiratory failure or hemodynamic instability.
  • Arrange interfacility transfer for specialized care if required.
• Begin management of SVC syndrome if present (see “Acute management checklist for SVC syndrome”).
• Manage compressive spinal emergencies if present.
• Obtain diagnostic investigations once clinically stable (see “Diagnostics”).
• Manage the identified underlying cause.
• Manage any complications of mediastinal masses.

Avoid procedural sedation and analgesia in children with anterior mediastinal masses (unless guided by a pediatric anesthesiologist) as it can cause fatal airway obstruction. ^[6]

Red flags in mediastinal masses ^[5]

Consult anesthesia and thoracic surgery early if any of the following red flag features of perioperative complications are present, especially in children.

• Signs of airway compromise
  • Stridor
  • Wheezing
• Signs of respiratory distress
  • Cough worsening in the supine position
  • Orthopnea
• Cardiovascular compromise
  • Syncope or presyncope
  • Edema of the head and neck, thorax, and/or upper limbs
• Imaging findings
  • > 70% reduction of tracheal luminal patency
  • Compression of the carina, major bronchi, or great vessels
  • Features of pericardial effusion

Respiratory support for mediastinal masses ^[5]

The following applies to patients with respiratory distress or respiratory failure due to compression of the upper airway or lower airway.

• Provide supplemental oxygen.
• Avoid supine positioning; consider lateral decubitus positioning or prone positioning (if feasible).
• Initiate CPAP if oxygen and positioning are insufficient.
• If respiratory failure requiring intubation and positive pressure ventilation is anticipated:
  • Consult anesthesia immediately.
  • Intubation past the level of obstruction may be necessary (e.g., using a tracheal tube or rigid bronchoscopy).
  • Avoid neuromuscular blockers for intubation.

Hemodynamic support for mediastinal masses ^[5]

The following applies to patients with obstructive shock due to compression of the great vessels or cardiac tamponade.

• Begin immediate hemodynamic support with IV fluid resuscitation.
• Avoid supine positioning; consider lateral decubitus positioning or prone positioning (if feasible).
• Manage cardiac tamponade if present.
• Consult anesthesia and thoracic surgery, as urgent surgical decompression may be required.

• Airway obstruction
• Obstructive pneumonia or atelectasis
• Pleural effusion
• SVC syndrome
• Cardiac tamponade
• Spinal cord compression
• Horner syndrome
• Esophageal compression
• Paraneoplastic syndromes (e.g., Lambert-Eaton myasthenic syndrome, hypercalcemia, SIADH)

We list the most important complications. The selection is not exhaustive.