Pallor fever
Purpura Neck, supraclavicular or
generalized adenopathy
Cough, dysphagia, hoarseness, new or refractory wheezing, dyspnea, orthopnea, facial swelling, and/or plethora Symptoms leading to chest X-ray
Mediastinal mass Nl CBC
Chest CT
(see ‘Assessment of a child with suspected leukemia’, p 74) Chemotherapy Chemotherapy ± radiotherapy Surgery ± radiotherapy Surgery Chemotherapy Surgery Radiation Diagnosis dependent Leukemia or lymphoma with marrow involvement Hodgkin Benign tumor NHL
Thymoma Mature teratoma
Chemotherapy Surgery Immature teratoma Neuroblastoma Neurofibroma Neurofibrosarcoma Schwannoma Lymphoma Ganglioneuroma Ewings sarcoma Rhabdomyosarcoma Benign masses Abnormal CBC
Blasts on blood smear Chest X-ray (AP and lateral)
Superior vena cava syndrome
(see ‘Recognition and management of superior vena cava syndrome’, p 96) Bone marrow aspirate ± biopsy
Large anterior mass
Bone marrow CT (abdomen/pelvis) Gallium/PET Bone scan Anteromedial mass AFP HCG Biopsy Posterior mass MRI spine Urine VMA/HVA Biopsy
Negative AFP and/or HCG Positive AFP and/orHCG
Lymphoma
Positive urine VMA/HVA Negative urine VMA/HVA Germ cell tumors
M. Weyl Ben Arush · J.M. Pearce
Assessment of a mediastinal mass77
–– See algorithms on generalized and localized lymph- adenopathy for additional details of clinical presentation. Cancerous nodes are generally very firm and fixed to underlying structures. It is often possible to discern several different nodes matted together. They are not warm, tender or fluctuant and do not respond to antibiotics. Supraclavic- ular adenopathy is most often associated with malignancy.
–– It is important to assess the airway with any antero- medial mediastinal mass – airway compression can be a life-threatening emergency. On plain chest X-ray the thymus may look like a mediastinal mass, but it has a characteristic shape and does not cause tracheal deviation. Presence of paratracheal and mediastinal adenopathy increases the suspicion of malignancy.
–– Evaluation of chest masses by CT scan is usually suf- ficient, especially with the high resolution and thin sections of spiral CT when available. MRI is valuable in defining posterior mediastinal masses and potential spinal canal involvement, which is an oncologic emergency to preserve neural function.
–– Diagnosis is confirmed by bone marrow examination. The arbitrary line between leukemia with adenopathy vs. lymphoma with marrow involvement is the percentage of blasts in the marrow. Greater than 25% blasts is defined as leukemia. T cell ALL is the leukemia most commonly asso- ciated with mediastinal masses, usually with a high WBC count.
–– Emergency low-dose radiation is indicated when there is life-threatening airway compromise from tracheal compression. Tissue radiation can make the pathologic diagnosis difficult. Ideally, biopsy of the mass occurs before radiation or from a node outside the radiation field. Chemo- therapy can also be used before a biopsy, but within 24– 48 h all of the tumor will be affected and it may be difficult to impossible to make a pathologic diagnosis thereafter.
–– Mediastinal non-Hodgkin lymphoma is most com- monly of T cell phenotype. It is possible to make the diag- nosis from pleural fluid or bone marrow if those tissues are involved. Evaluate the spinal fluid for malignant involve- ment. Except for emergency radiation for the airway, thera- py is based on chemotherapy alone.
–– 20–30% of children present with B symptoms (night sweats, weight loss of >10% body weight, and/or fevers >38°C). Nodes are generally not painful or tender but have a ‘rubbery’ firmness, and often have a variable growth rate. Gallium scan is positive in 40–60% of the cases and can be used to follow the disease response with treatment, but it is also positive in many nonmalignant inflammatory condi- tions. PET scanning is gaining favor as it is more specific to identification of lymphoma sites and as a marker of disease response is more highly predictive of cure.
–– Benign tumors are usually located in the anterome- dial mediastinum: bronchogenic cysts, goiter, lipoma, lymphangioma, and enteric cysts are the most frequent and are diagnosed by open biopsy. In the posterior mediastinum, neurenteric cysts are generally associated with congenital abnormalities of the thoracic spine. The CT findings will often suggest these diagnoses.
–– Nearly one-half of these tumors are asymptomatic, but up to 30% of all patients, with or without symptoms, can have myasthenia gravis. The histologic diagnosis is made through open biopsy or mediastinoscopy. Treatment is surgical excision.
–– These tumors are usually asymptomatic until they reach a considerable size and may produce tracheal and bronchial compression. Tumor markers such as ␣-fetopro- tein (AFP) and human chorionic gonadotrophin (HCG), both detected in serum, may be the only clues to diagnosis. Interpreting AFP in infants can be difficult as they normally have a high level at birth and a variable half-life. Mature teratomas are negative for these markers and, therefore, the presence of a positive marker indicates a malignant component within the mass. A biopsy, open or by medi- astinoscopy, is necessary to differentiate the subtype of germ cell tumor although treatment is currently the same for all groups. Completely mature teratomas respond only to surgical resection.
–– Posterior masses adjacent to the vertebra can invade the spinal cord. If the cord and clinical function are compro- mised it is possible to preserve neurologic function by im- mediate initiation of chemotherapy, spot radiation or surgi- cal laminectomy with removal of tumor.
–– Elevation of urinary HVA and/or VMA can be diagnos- tic of neuroblastoma. Minor elevations can be due to diet intake, as phenylalanine and tyrosine raise these levels. To be significant they should be 3 SD above the mean. VMA and HVA can be measured on spot urine samples by nor- malizing them against creatinine levels on the same sample.
–– Neuroblastoma in the posterior mediastinum tends to be stage I–III with more histologic differentiation and a decreased rate of metastases. Surgical removal can be diffi- cult because of adjacent vital structures. The posterior me- diastinum is also the most common site of a fully mature ganglioneuroma (often VMA/HVA negative) as well as gan- glioneuroblastoma.
–– Neurofibroma, neurofibrosarcoma, and malignant schwannomas are all derived from the neural crest and are most commonly seen in patients with neurofibromatosis. Enteric cysts and thoracic meningoceles are very rare. Very rarely, Ewing and rhabdomyosarcoma occur in the posteri- or mediastinum.
Selected reading
For chapters on non-Hodgkin lymphoma, Hodgkin disease, acute lymphoblastic leukemia and neuroblastoma see Emedicine Pediatric Medicine, E medicine, 2002 (http://emedicine.com).
Hudson MM, Donaldson SS: Hodgkin’s disease. Pediatr Clin North Am 1997;44:891–906. Shad A, Magrath I: Non-Hodgkin’s lymphoma. Pediatr Clin North Am 1997;44:863–890. Strollo DC, Rosado de Christenson ML, Jett JR: Primary mediastinal tumors. I. Tumors of the anterior mediastinum. Chest 1997;112:511–522.
Strollo DC, Rosado de Christenson ML, Jett JR: Primary mediastinal tumors. II. Tumors of the middle and posterior mediastinum. Chest 1997;112:1344–1357.