19. Tumors of the mediastinum; mediastinitis

Tumours of the mediastinum and mediastinitis

The mediastinum is divided into superior and inferior compartments; the inferior mediastinum is commonly subdivided into anterior, middle and posterior regions.
Anterior mediastinal masses classically include thymic lesions, lymphoma, thyroid-related masses and germ-cell tumours. Middle lesions include bronchogenic/pericardial cysts and lymphadenopathy. Posterior lesions commonly include neurogenic tumours and foregut duplication cysts.
Age, exact compartment, CT appearance and associated symptoms help narrow the diagnosis. Some lesions are incidental; others compress the airway, vessels, oesophagus or heart.

Symptoms include chest pain, cough, dyspnoea, dysphagia, hoarseness, stridor, superior vena cava obstruction, fever or weight loss. Myasthenic symptoms may accompany thymoma.
Chest radiograph may show mediastinal widening or a mass. Contrast CT defines compartment, fat, calcification, cystic/solid components, invasion and vascular relationships.
MRI helps define cystic lesions, neural involvement and vascular or cardiac relations. PET-CT is useful for selected lymphoma or staging questions.
Blood tests may include AFP, beta-hCG and LDH when germ-cell tumour is suspected; thyroid tests or autoimmune assessment are guided by presentation.
Tissue diagnosis is required for many solid lesions, but biopsy approach must be planned carefully. Suspected resectable thymoma may proceed to surgery without needle biopsy in selected cases because capsular violation is undesirable.

Management depends on histology, stage, symptoms and resectability. Resectable thymoma is usually treated surgically; radiotherapy or systemic therapy may be added for invasive or advanced disease.
Lymphoma is generally treated with systemic therapy rather than primary surgical excision. Germ-cell tumours require histology-specific chemotherapy and/or surgery.
Symptomatic cysts may require excision or drainage depending on type and complications. Neurogenic tumours are often resected when appropriate.
Airway or vascular compression requires urgent specialist assessment and careful anaesthetic planning. Complications include SVC syndrome, airway compromise, pericardial involvement and recurrence.

Mediastinitis is infection/inflammation of mediastinal tissues. Causes include descending spread from deep neck infection, oesophageal perforation, postoperative infection after sternotomy and penetrating trauma.
Features include severe chest or neck pain, fever, toxicity, dyspnoea, dysphagia and sepsis. Cervical crepitus may occur with oesophageal perforation.
Contrast CT neck/chest is the key investigation to identify mediastinal gas, fluid, fat stranding and the source. Blood cultures and source cultures guide antimicrobial therapy.
Treatment is an emergency: resuscitation, broad-spectrum IV antibiotics covering aerobic and anaerobic organisms, urgent source control and drainage/debridement. Oesophageal perforation requires prompt specialist management. Delayed treatment carries high mortality.