Solid Chest (Medistinal) Tumors

Mediastinal tumors are fairly common in children and can be either benign (noncancerous) or cancerous (malignant). Approximately 60% are malignant. These tumors include Hodgkin’s disease, non-Hodgkin’s lymphoma, neurogenic tumors, thymomas, teratomas, lipomas, lipoblastoma, germ cell tumors, and other rare lesions. Hodgkin’s disease and non-Hodgkin’s lymphoma are the most frequently observed mediastinal tumors (Table 1).

Table 1.Mediastinal Tumors in Children - Number of Cases
Tumor Type	Simpson (1991)	Saenz et al (1993)	Cohen et al (1991)	Grosfeld et al (1994)	Total
Neuroblastoma	16	32	13	50	111
Ganglioneuroma	9	14	8	14	45
Neurofibroma	4	3	—	2	9
Neurilemoma	1	3	1	5	10
Pheochromocytoma	—	2	—	—	2
PNET	—	2	—	2	4
Hodgkin’s disease	29	34	1	49	113
NHL	34	6	3	38	81
Teratoma (benign)	7	2	4	18	31
Germ cell tumor	—	—	—	3	3
Thymoma	—	—	2	3	5
Thymic carcinoma	1	—	1	1	3
Cystic hygroma	3	1	3	11	18
Lipoma	—	3	1	3	7
Lipoblastoma	—	—	—	2	2
Rhabdomyosarcoma	—	—	—	1	1
Fibroma	—	—	—	1	1
Hemangioma	—	—	—	1	1
Hamartoma	—	—	—	1	1
Total	104	102	37	205‡	448

*Lymphoid tumors are the most common mediastinal tumor in the pediatric age group (194/448 = 43.3%). Posterior mediastinal neurogenic tumors are the second most common group of tumors (181/448 = 40.4%), whereas teratomas and germ cell tumors are the third most frequently observed neoplasms (34/448 = 7.5%).
†Data from Simpson I, Campbell PE: Prog Pediatr Surg 27:92, 1991; Saenz N, et al: J Pediatr Surg 28:172, 1993; Cohen AJ, et al: Ann Thorac Surg 51:378, 1991; Grosfeld JL, et al: Ann Surg Oncol 1:121, 1994.
‡Nine additional cases added to this review.
PNET, primitive neuroectodermal tumor; NHL, non-Hodgkin’s lymphoma.

About 40% to 60% of children with Hodgkin’s disease present with a mediastinal mass in the front of the chest. The mass may show up with coughing, wheezing, or severe breathing problems. In general, the surgeon’s involvement with these patients is to provide a piece of the mass for diagnosis. Treatment is nonsurgical and involves chemotherapy and radiation. Children with non-Hodgkin’s lymphoma may present with a mediastinal mass in 25% to 30% of cases. They present with breathing problems, pleural effusion, and occasionally superior vena caval syndrome in which the main vein draining the blood from the upper body into the heart is blocked (5% to 6%). It is preferable to obtain a biopsy from a nonmediastinal source, such as bone marrow aspirate, pleural fluid, or lymph node tissue, to make a diagnosis and avoid a general anesthetic. That may not always be possible, and open biopsy of the mediastinum under general anesthesia may be required.

In patients with a large mediastinal mass, one worries about cardiac arrest once anesthesia is started. A CT scan of the chest documenting a tracheal area of greater than 50% of normal and pulmonary function tests that show a the ability of the patient to breathe at greater than 50% of predicted are preoperative indicators that anesthesia may be tolerated without tracheal collapse and cardiac arrest. In patients with mediastinal lymphomas, echocardiography is the best tool for evaluation to rule out problems with heart function. If heart function is abnormal, these patients should be treated without biopsy. Therapy includes chemotherapy and occasionally bone marrow transplantation.

As a group, neurogenic tumors are the second most common chest tumors of infancy and childhood (see Table 1). The benign tumors—ganglioneuromas, schwannomas, and neurofibromas—may enlarge without producing any symptoms until a Horner’s syndrome occurs (the pupil becomes large and the eyelid sags on the side of the tumor) or significant airway (tracheal) pressure produces breathing problems. Neuroblastoma is a highly cancerous tumor with approximately 20% occurring in the back of the chest. In a third of cases, the tumor may be asymptomatic and is identified by its presence on a chest x-ray. In some instances, the tumor presses on the lung and causes breathing problems. Pain may occur because of involvement of nerves or symptoms from distant spread of the cancer (particularly spread to the bone). Occasionally the neuroblastoma may erode the ribs and extend through the chest wall, producing a visible mass on the outside. Extension of tumor into the spinal canal may occur causing neurologic problems (10% to 15%).

Ganglioneuroma

Ganglioneuromas are the most common neurogenic chest tumors of childhood. Most cases have been reported in infants and children. These tumors can become large. The tumor cells have their origin from the sympathetic chain which runs down either side of the spine. These tumors frequently widen the spaces between the ribs and can extend into the spinal canal. Because they are well encapsulated (have a good capsule around them) they usually can be removed. In rare cases, ganglioneuromas are the result of a neuroblastoma changing from a cancer to a benign tumor.

Figure 1: A large ganglioneuroma (arrows) being removed from the chest.

Neurofibroma and Neurilemoma

Neurofibromas arise from the nerves in the back of the chest. They may be one of multiple tumors related to neurofibromatosis (von Recklinghausen’s disease). Scoliosis (curvature of the spine) is often found. The isolated tumors are well encapsulated and usually readily removed. However, the tumors associated with neurofibromatosis tend to extend along the nerves so that total removal is often impossible. They can change to a cancer, but usually this takes place in large tumors and in older patients. Neurilemoma (schwannoma) also arises from nerve sheaths and similarly can be benign or malignant.

Neuroblastomas

Neuroblastomas are malignant (cancerous) tumors arising from cells of the sympathetic nerve chain or the adrenal gland. Most neuroblastomas in infancy and childhood are found in the back of the abdomen (retroperitoneum: adrenal [50%], paraspinal [20%]). Tumors can arise in the back of the chest in 20% of cases and the neck and pelvis in the remaining 10%. Elevated levels of substances in the urine known as catecholamines or their byproducts such as vanillylmandelic acid and homovanillic acid (usually elevated) can suggest the diagnosis. The tumor appearance on x-ray usually shows a tumor next to the spine in the back of the chest which contains fine calcium. The tumor spread can be clarified by a CT scan. A nuclear medicine test known as the metaiodobenzylguanidine (MIBG) scan also has been used to diagnose this tumor and evaluate for the presence of bone spread.

Figure 2: Abdominal neuroblastoma being removed.

Neuroblastomas can be dumbbell-shaped and extend into the spinal canal. Magnetic resonance imaging (MRI) is useful in detecting intraspinal extension. Complete removal is often not possible; however, even with an incomplete removal leaving small amounts of tumor near the spine, the prognosis for lesions arising in the chest is much better than that observed in patients with neuroblastomas in the abdomen. The overall survival for children with a mediastinal primary is 80%. The findings at operation and evaluation of the genetic characteristics of the tumor tissue (increased amounts of the n-myc gene) often determine a worse outcome as does age greater than 1 year at diagnosis.

Teratoma

Teratoma is the third most common mediastinal tumor (Figure 3). Teratomas almost always are located in the front of the chest. They can be benign or malignant (20%), can be solid or cystic, and contain all three types of fetal developing tissue (endoderm, mesoderm, and ectoderm). Teratomas also may involve the pericardium (sac around the heart). On a chest x-ray or CT scan of the chest calcifications (occasionally teeth) noted in a tumor in the front of the chest are consistent with a diagnosis of teratoma until proven otherwise. Benign lesions almost always can be removed, whereas malignant lesions often can’t because of invasion of surrounding structures in the chest. In the neonatal period, benign teratomas occasionally may be the cause of life-threatening breathing problems. Malignant teratomas are often sensitive to chemotherapy programs that can shrink a tumor that could not be removed and occasionally allow for subsequent removal. Delayed attempts at removal after chemotherapy administration is also effective treatment. Occasionally a germ cell tumor of the chest may present with early puberty in boys with Klinefelter’s syndrome. Patients with malignant teratomas or germ cell tumors often have elevated serum α-fetoprotein levels and may have an elevated serum β-human chorionic gonadotropin level. Removal of the entire tumor is the strongest predictor of survival. The current survival for mediastinal teratoma tumors is greater than 85%.

Figure 3: Computed tomography scan shows a large teratoma on the left next to the heart (arrows).

Thymoma

Thymomas are tumors of the thymus gland and are extremely rare in children. They are managed in the same manner as they are in adults. An enlarged thymus in early infancy can look like a tumor and result in breathing difficulties. The fact that enlargement of the thymus gland in this age group is almost never due to a cancerous process should encourage either continued observation or a brief course of steroids to shrink the size of the gland. Thymolipoma is a benign tumor of the thymus that can be diagnosed in infants and children.