Applied Radiology

Prepared by Phillip J. Haney, MD, Department of Diagnostic Radiology, University of Maryland School of Medicine, Baltimore, MD.

PROBLEM:

A newborn infant was found to have a large chest mass. An unenhanced CT scan through the lower thorax (figure 1) was obtained. T2-weighted MR images (figures 2,3) also are shown. What is the most likely diagnosis?

ANSWER:

Congenital neuroblastoma

DISCUSSION:

Neuroblastoma is the most common of those rare solid malignancies that may present at birth. The tumor develops in utero when primitive neuroblastic cells fail to undergo normal regression and differentiation. It may cause hypertension, preeclampsia, hydrops, or hydramnios. Metastases to the placenta or umbilical cord may occur, but spread to the maternal circulation has not been described.

In the case presented here, a large calcified mass was found in the posterior right chest on the CT scan (figure 1). Up to 85 percent of neuroblastomas will be calcified on CT. The T2-weighted MRI images (figures 2,3) show a hyperintense mass in the posterior right hemithorax adjacent to the spine. MR images usually will demonstrate prolonged T1 and T2 relaxation times. Additionally, the disorder can be detected on routine prenatal sonography.

Although most congenital neuroblastomas present as adrenal masses, thoracic and cervical tumors also may occur. An adrenal tumor is shown in figures 4 and 5--unenhanced and enhanced CT scans of another newborn with a palpable abdominal mass. This large retroperitoneal mass is calcified and prevertebral in location, contiguous to the aorta. These signs, along with involvement or encasement of the arteries and veins, are characteristic of neuroblastoma both in neonates and in older children. The tumor may grow along the vascular pathways and invade the kidneys, or may spread to retroperitoneal nodes.

Congenital neuroblastoma may present with metastases, most commonly to the liver, bone marrow, and skin. An example of hepatic spread is shown in figure 6. Here, there is a left neuroblastoma (N) and a markedly enlarged liver with heterogeneous attenuation. In this case, the large liver obscured the adrenal mass on physical examination. The liver may be involved to such an extent that it leads to respiratory compromise or hepatic failure.

Cystic morphology of congenital neuroblastoma is an unusual finding and ranges from small cysts to large, thick-walled cysts with fluid levels. Cystic metastases to the liver also may be seen. The diffuse pattern of liver involvement shown in figure 6 is typical for malignant involvement in the very young; older patients tend to have nodular involvement.

Both isolated and metastatic congenital neuroblastomas have a relatively good prognosis in infancy compared to tumors in older children. Favorable prognostic indicators include low stage of disease, favorable biologic markers, and histopathology compatible with neuroblastoma in situ. Those infants with metastatic disease tend to fall into Stage IV-S with involvement of the liver, marrow, and skin. Overall survival varies from 60 to 90 percent with Stage IV-S tumors, compared to 95 to 100 percent in Stage I disease. Therapy generally consists of tumor resection only; chemotherapy is reserved for patients with recurrent, progressive, or disseminated disease.