Mediastinal Masses

Abstract

Mediastinal masses are varied and present at all ages, from newborn to adolescence. There is a wide spectrum of pathology that may include congenital, inflammatory, infectious, and neoplastic processes. Because of the limited space and confined geometry of the region, masses can interfere with both the respiratory and cardiovascular systems, sometimes with grave results. Urgent consultations from oncologists and pediatric intensivists are common, and most of these patients will require some form of surgical intervention, such as biopsy, resection, or venous access. Applicable techniques range from minimally invasive procedures to large thoracotomy or sternotomy. Expertise with these procedures as well as a detailed knowledge of the anatomy and wide range of pathology of the region are essential. An in-depth understanding of the decision-making regarding pre-anesthetic work-up and management can help prevent potentially disastrous complications.

Appendices

Summary Points

Pediatric surgeons must be well-versed in the anatomy and range of pathology in the mediastinum.

The lesion must be assessed by plain radiographs, CT, and sometimes MRI to help with differential diagnosis.

Consultation with an experienced pediatric radiologist can be very helpful with creation of a differential diagnosis, assessing airway patency, and surgical planning.

Close interaction with pediatric oncology team is important to formulate a cohesive plan for biopsy or resection.

For biopsy, always search for least morbid procedure to achieve desired result.

The pre-anesthesia work-up is key to avoid serious airway complication prior to any operative intervention involving anesthesia.

Operative strategies include minimally invasive (thoracoscopy, mediastinoscopy) or open (thoracotomy, median sternotomy).

Editor’s Comment

Mediastinal masses are quite variable in their origin, diagnostic work up, and therapeutic approach. There are a handful of lesions that we commonly see in children but there are also many that are unusual and require a thoughtful and often multidisciplinary approach to management. Regardless of the diagnosis, it is extremely important for the pediatric surgeon to have absolute command of the intricate anatomy of the mediastinum, including all known variations thereof, especially before embarking on an attempt at resection. Biopsy or removal of apical paraspinous lesions places the stellate ganglion at risk, which can result in Horner syndrome (ipsilateral enophthalmos, small pupil, ptosis, dry eye). This is sometimes unavoidable and expected (neuroblastoma resection) and parents need to be warned in advance that it is likely to be permanent. The phrenic nerve is always at risk and should be clearly identified and protected throughout the course of any operation in the chest. The recurrent laryngeal nerve can also be injured and its anatomic course should be anticipated. Finally, thoracic duct injury can occur unexpectedly and results in significant postoperative morbidity. After resection of a mass or dissection anywhere in the mediastinum, the tissue bed should be examined carefully for leakage of lymphatic fluid, which will be clear in the patient who has fasted. If the source is not visible, infusing a small amount of cream into the GI tract by nasogastric gastric tube can be helpful.

Rapidly expanding lymphoma that presents as an anterior mediastinal mass can be challenging due to the risk of sudden airway collapse after induction of anesthesia or even sedation. An alternate means of obtaining diagnostic material should be sought: cervical lymph node biopsy, drainage of pleural fluid for cytology, bone marrow biopsy, US- or CT-guided percutaneous core needle biopsy under minimal sedation and local anesthetic. If general anesthesia is truly the only option, which is rarely the case, contingencies should be made for possible cardio-pulmonary bypass or ECMO should airway collapse become a reality. Clearly, this is a situation that is best avoided if at all possible.

Foregut duplications, thymic masses, and paraspinous ganglioneuromas are nearly always safely resectable by thoracoscopy and this should be the standard approach for each of these lesions. Likewise, biopsy of almost any mediasatinal lesion, including paratracheal and subcarinal lymph nodes, can be performed safely using a minimal-access approach. Because the resultant scar is frequently cosmetically unappealing, the Chamberlain operation should only be used if there is truly no other approach available. For large lesions or malignant lesions, the posterolateral thoracotomy is standard, but a muscle-sparing approach should always be used. The pediatric general surgeon should also be comfortable with performing a sternotomy when necessary for large midline lesions (mediastinal teratoma). It is safe, offers excellent exposure, provides for a very stable closure, and is extremely well-tolerated (in most cases, better than a large thoracotomy!). The only real disadvantage is the scar. Finally, the axillary approach can be useful in certain cases, especially when dealing with lesions near the apex. A transverse incision is placed in the lowest axillary skin crease between the pectoralis major and latissimus dorsi muscles and the chest is entered through the third intercostal space. An extrapleural approach can be used in some cases. The principle limitations of this approach are limited exposure and the inability to extend the incision.

Differential Diagnosis

Anterior (often neoplastic)

• Lymphoma

• Germ cell tumor

• Thymic cyst/thymoma

Middle (often cystic)

• Congenital foregut malformation

Posterior: usually neural

• Ganglioneuroma

• Neuroblastoma

Diagnostic Studies

• Chest X-ray

• CT scan

• ± MRI (depending on location)

• Pulmonary function tests for anterior mediastinal mass

• Appropriate tumor markers as indicated by clinical suspicion

  • AFP

  • HCG

  • Urine for catecholamines and metanephrines

Preoperative Preparation

• Airway assessment

• Type and screen

• Informed consent regarding potential injury to great vessels, airway, thoracic duct, nerves, likelihood and duration of chest tube