Neuroblastoma

A 9-month-old girl was brought to the emergency department (ED) by her mother for abdominal distention, progressive failure to thrive, diarrhea, and occasional vomiting. At her 6-month well-child check-up, the infant had been at the 50th percentile in weight; now she was at the 10th percentile. She was afebrile.

Supine and decubitus views of the patient’s abdomen were ordered.

1. What do these radiographs show?A. Small-bowel obstruction.
B. Bowel perforation.
C. Malrotation.
D. Other.

1. What do these radiographs show? (D is the correct choice.)

The bowel gas pattern is not 100% normal. Many loops of distended bowel are present, both in the small bowel and in the colon. There are also air-fluid levels. However, the pattern does not truly reflect an obstruction (although enteritis is a consideration), nor is perforation demonstrated. The condition suggested by the important abnormality seen here is not listed as an option.

2. Heightened suspicion, based on the patient’s marked failure to thrive and the radiographic findings, led to a workup for Hirschsprung disease. This is a postevacuation image from her contrast enema.

What is your impression of this image?

A. The contrast enema was complicated by perforation.
B. It raises reasonable suspicion for Hirschsprung disease
C. It definitively excludes Hirschsprung disease.

Answer on next page

Answer to Question 2 and Discussion

2. What is your impression of this image? (B is the correct choice.)

On the basis of the contrast enema and the observation that the caliber of the sigmoid colon is slightly greater than the caliber of the rectum, suspicion for Hirschsprung is reasonable. However, the patient underwent a rectal biopsy that revealed normal ganglion cells, thereby excluding Hirschsprung disease.

3. To clarify an earlier observation, these frontal and lateral views of the chest were obtained.

What finding evident in these films suggests a unifying diagnosis?

A. Mediastinal mass.
B. Upper lobe pneumonia.
C. Rounded atelectasis and volume loss.

3. What finding evident in these films suggests a unifying diagnosis? (A is the correct choice.)

There is a calcified left posterior mediastinal mass. Its position on the lateral view, along with the widening of the spaces between the ribs posteriorly at that level, indicates a posterior location; the widening of the spaces between the ribs is caused by the effect of the mass on the ribs near their articulation with the thoracic vertebral bodies.

In retrospect, the mediastinal mass can be seen on the original abdominal radiographs that were obtained to evaluate for diarrhea and abdominal distention. The coarse calcifications and posterior mediastinal location suggested the diagnosis of neuroblastoma, which was later confirmed (stage 2B). Note the subtle widening of the intercostal spaces between the fourth, fifth, and sixth posterior ribs. The discovery of the neuroblastoma provides an explanation for the failure to thrive and the diarrhea. Subsequently, further workup with I-131 metaiodobenzylguanidine (MIBG), CT, and MRI of the spine was ordered.

Neuroblastoma is one of the most common tumors of early childhood. It has been variably described as the most common malignancy of the neonatal period, the most common solid extracranial tumor in children, the third most common malignancy of childhood overall, and the second most common abdominal tumor of childhood after Wilms.^1-3 It accounts for about 10% of all childhood cancers.^1,2

Neuroblastoma and its cousins, ganglioneuroblastoma (somewhat less aggressive) and ganglioneuroma (benign), arise from neural crest tissue. Thus, neuroblastoma may arise anywhere that sympathetic nerve tissue is found, which means anywhere between the upper cervical region and the lower sacral region.

The typical age range for newly diagnosed neuroblastoma is 0 to 5 years, although it may be seen as late as the teenage years and has also been identified in utero via fetal MRI and prenatal ultrasonography. The median age of a child with newly diagnosed neuroblastoma is slightly under 24 months.^1,2

Symptoms of neuroblastoma. A nonspecific or misleading initial clinical presentation is not uncommon; patients may present with any of the following symptoms, depending on the location and size of the tumor: back pain, bone pain, bowel or bladder incontinence or retention, weight loss, abdominal distention, extremity weakness, proptosis, hoarseness, hypertension, renal atrophy, edema, irritability, scoliosis, stridor, superior vena cava syndrome, dyspnea, dysphagia, limping, or hepatomegaly.^1,2 Patients may also have a variety of symptoms related to paraneoplastic effects (such as opsoclonus myoclonus) or resulting from secretion of excess hormones (such as vasoactive intestinal peptide [VIP] and catecholamines). It is known that excess VIP can cause diarrhea and hypokalemia, both of which were present in this patient.²

Radiographic findings. Several imaging modalities are commonly used in the evaluation of a child with suspected or confirmed neuroblastoma. Often, in a child who presents with nonspecific symptoms, radiographs or ultrasonography may be the first imaging study ordered. On radiograph, neuroblastoma tumors very commonly demonstrate calcifications. Although these calcifications are often coarse and “chunky” in appearance, as they are in this patient (A), they may also be powdery, wispy, or lobular-or may appear as fine speckles. A high degree of suspicion is warranted whenever unexplained calcifications are seen on the radiograph of a child, particularly in the chest or abdomen. Neuroblastoma may also have cystic or necrotic areas, and the enhancement pattern may be inhomogeneous.

Although an ultrasonogram may contribute to the imaging evaluation, ultrasonography alone is insufficient for complete assessment of disease. Features of neuroblastoma that need to be considered include the tumor’s full size, its relationship to vessels, other organ involvement (invasion or distant metastases), osseous metastases, nodal disease, and potential extension of the tumor into the spinal canal. (As a rule of thumb, neuroblastoma typically displaces the kidney and encases local vessels; in contrast, Wilms tumor infiltrates the kidney but displaces vessels, rather than encircling or encasing them.)

Role of MRI and CT. For the level of detail required for complete assessment, enhanced MRI or CT is used. A posterior mediastinal mass is clearly visible in an axial enhanced chest CT image in this patient (B). The advantage of MRI over CT is that MRI affords superior detection of bone marrow involvement; MRI is also recommended for patients with paraspinal tumors, to assess for potential spinal involvement.^1,2 CT is often the modality chosen for long-term follow-up in patients who have undergone surgery or received chemotherapy.

Nuclear medicine studies. MIBG is often used for initial identification and surveillance. In this patient, a coronal image from MIBG (C) reveals expected physiological activity in the liver, salivary glands, and bladder, as well as showing the posterior chest mass (arrow). However, nuclear medicine studies will miss up to 30% of neuroblastic tumors because of inherent individual tumor characteristics.2 Technetium 99m methylenediphosphonate scintigraphy (also known as a “bone scan”) is typically used at the time of diagnosis to assess bone disease.²

Outcome of this case. In this infant, complete surgical excision of the tumor was achieved. She remains disease-free 7 months later.

References:

REFERENCES:1. Siegel MJ, Jaju A. MR Imaging of neuroblastic masses. Magn Reson Imaging Clin N Am. 2008;16:499-513.
2. Lonergan GJ, Schwab CM, Suarez ES, Carlson CL. Neuroblastoma, ganglioneuroblastoma, and ganglioneuroma: radiologic-pathologic correlation. Radiographics. 2002;22:911-934.
3. Daneman A. Adrenal gland. In: Kuhn JP, Slovis TL, Haller JO, eds. Caffey’s Pediatric Diagnostic Imaging. 10th ed. Philadelphia: Mosby; 2004:1894-1908.