Radiology Cases in Pediatric Emergency Medicine Volume 7, Case 12 Muhammad Waseem, MD

This is a 13 year old male with a chief complaint of bilateral scrotal swelling. The swelling began a month ago and has been gradually increasing. It is associated with mild discomfort but no pain. He complains of fatigue and two episodes of epistaxis in the last month. There is no history of trauma or voiding difficulties. Review of systems are otherwise negative for fever, chills, headache, cough, abdominal pain, weight loss or night sweats. He has no other significant past medical history.

VS T 36.7 (oral), P 84, R 18, and BP 110/70. He is healthy appearing and comfortable. He has significant bilateral scrotal swelling with the skin taut and erythematous. The right hemiscrotum measures 8 cm x 4 cm. The left hemiscrotum is 8.5 cm x 4 cm. The scrotal swelling is firm, non-tender and does not transilluminate. There is no clinical evidence of organomegaly, lymphadenopathy or an abdominal mass. The remainder of the physical examination is normal. His WBC is 4,300 with 24% neutrophils, 64% lymphocytes and 3% eosinophils. A review of the peripheral smear is negative for blast cells. Since systemic diseases such as lymphoma may present as a testicular mass, a chest radiograph was obtained.

His chest radiographs reveal an anterior mediastinal mass. The PA view shows a widened mediastinum. Note the abnormal contour of the mediastinal shadow above the heart. The lateral view shows a solid tissue density in the region anterior and superior to the heart. In infants, this region is filled with a thymic density. However, in children, teens and adults, this region should be occupied by lung tissue. A solid tissue density is suggestive of a mediastinal mass (or right ventricular enlargement). The suggestion of a mediastinal mass in conjunction with testicular swelling suggests the presence of a neoplastic process. The common causes of testicular swelling with a mediastinal mass include lymphoma, leukemia and germ cell tumors.

His CBC does not show any signs of leukemia. Beta HCG and Alpha-fetoprotein, both markers for germ cell tumors, are normal. Testicular biopsy demonstrates the presence of a lymphoblastic lymphoma. Bone marrow examination does not show marrow involvement.

Lymphoma is the third most common neoplasm of childhood after leukemia and central nervous system (CNS) tumors (1). It is the most common anterior mediastinal mass accounting for a quarter of all mediastinal masses (2).

Pediatric Non-Hodgkin's lymphoma (NHL) accounts for approximately 10% of cancers in children and adolescents (3). The peak age of presentation is 9 years (2), and males outnumber females 3 to 1 (4). Non-Hodgkin's lymphomas can usually be placed in one of the three major subgroups: Burkitt's lymphoma, lymphoblastic lymphoma and large cell lymphoma (3). Patients with lymphoblastic lymphomas commonly manifest as an intrathoracic tumor, particularly as a mediastinal mass (50% to 70%) and often have pleural effusions (4). More than 70% of the patients have disseminated disease at the time of presentation (2).

Mediastinal masses are the most common thoracic masses in children. Approximately 30% develop before age 12. Approximately 30% occur in the anterior, 30% in the middle, and 40% in the posterior compartment of the mediastinum (2). The diagnosis of lymphoma should be made expeditiously, as it can disseminate rapidly. Diagnostic studies should include complete blood count, sedimentation rate, serum LDH, Beta HCG, alpha-fetoprotein and a chest radiograph. Early involvement of an oncologist is essential in order to facilitate an appropriate work-up.

Teaching points

1.Any patient with painless testicular swelling not associated with underlying inflammation, trauma or infection should have a chest radiograph to identify the presence of a mediastinal mass or parenchymal lung lesions.

2.The first step in evaluating a mediastinal mass lesion is to place it in one of the three mediastinal compartments, since each has its own differential diagnosis. The most common lesions in the anterior mediastinum are thymoma, lymphoma and teratoma. The most common masses in the middle mediastinum are vascular masses, lymph node enlargement from metastases or granulomatous disease and pleuropericardial and bronchogenic cysts. In the posterior mediastinum, neurogenic tumors, meningocele, meningomyelocele, gastroenteric cysts and esophageal diverticula are commonly found (5). Neurogenic tumors comprise 90% of the posterior mediastinal masses in the pediatric age group. Neuroblastoma is by far the most common followed by ganglioneuroblastoma and ganglioneuroma. Mediastinal neuroblastoma is also associated with a more favorable prognosis when diagnosed in a child before 1 year of age (2).

3.After identification of a mediastinal lesion on a conventional radiograph, CT or MRI is the preferred modality for further evaluation of the middle and anterior mediastinum, whereas MRI is definitely the preferred modality for posterior mediastinal lesions, since most are neurogenic lesions which delineate better with MRI because of its multiplanar capabilities (2).

Copyrighted:-Radiology Cases in Pediatric Emergency Medicine Volume 7, Case 12 Loren Yamamoto, MD, MPH, Professor of Pediatrics, University of Hawaii John A. Burns School of Medicine.Loreny@hawaii.edu