Neuroblastoma is the second most common intra-abdominal neoplasm after Wilms’ tumor and the third most common pediatric tumor after leukemia and tumors of the central nervous system (CNS), accounting for 10 % of all pediatric neoplasms [14]. The majority (75 %) of neuroblastomas arise in the abdomen, with one third of these in the adrenal glands. The remainder of the neuroblastomas can occur anywhere along the sympathetic nerve chain, from the neck to the pelvis [15]. Over 90 % of the patients present between 1 and 5 years (median 2 years). Prenatal diagnosis occurs more frequently due to a rising number of fetal imaging, and currently 20 % of all neuroblastomas are diagnosed prenatally or within the first 3 months of life [16].

Clinically, neuroblastoma most commonly presents as a palpable mass, but can be an incidental finding on US or sequential imaging. If symptomatic, children can present with signs of increased adrenal medullary hormone production or symptoms from direct tumor growth or metastatic disease.

Local invasion can occur into the liver, kidneys, and through the neural foramina into the spinal canal, causing cord compression symptoms. Neuroblastomas typically show encasement or displacement of the vascular structures and only rarely invade the vasculature or ureter, which can be helpful to distinguish them from Wilms’ tumor. Distant metastases are present in half the cases at the time of diagnosis and are most commonly found in lymph nodes, bone marrow, liver, and skin [7].

US is often the first diagnostic imaging tool applied and can also be helpful in the diagnosis of metastatic disease, especially in liver involvement. On US, the neuroblastoma usually appears as a heterogeneous mass, with hyperechoic areas caused by calcifications, with or without posterior acoustic shadowing. Hypoechoic and anechoic areas in neuroblastoma correspond to cystic, hemorrhagic, or necrotic changes and are less common than in Wilms’ tumor . Larger cystic areas are more often present in newborns, in whom bilateral cystic neuroblastoma with intracystic hemorrhage may occur (Fig. 14.2) [17].

Diagnosis of neonatal neuroblastoma is often more challenging for several reasons. Sonographic findings may resemble neonatal adrenal hemorrhage , and, in addition, tests specific to neuroblastoma such as metaiodobenzylguanidine (MIBG) scintigraphy and sampling of urine catecholamines are not reliable in this age group. Urinary catecholamines are increased in 90 % of the cases beyond infancy, but only in half of the cases in the first year of life. However, neuroblastoma in neonates usually shows a 4-year survival of greater than 95 % and is associated with a high rate of spontaneous regression, so that an expectant approach with serial short-term follow-up US with Doppler is often the only recommended testing [18]. If the mass does not decrease in size or enlarges, and/or shows increasing echogenicity, a more aggressive form of neuroblastoma should be considered [19].

Other differential diagnoses in the neonatal period include intra-abdominal extralobar pulmonary sequestrations. Helpful hints are the location and morphology, with sequestrations being more commonly located in the left suprarenal region, while neonatal neuroblastoma is more commonly located on the right side and is more heterogeneous in morphology. Calcifications occur in neuroblastoma and have not been reported in sequestrations. Additionally, feeding arteries are common in sequestrations. Neuroblastoma does not occur prior to the third trimester of gestation because the neural tissue in the adrenal gland is too underdeveloped to give rise to neuroblastoma, therefore alternative diagnoses should be considered in an adrenal region mass discovered in this age group [7].

Ganglioneuroblastomas arise from both, the mature ganglion cells and immature cells resembling neuroblastoma cells, resulting in a potentially malignant behavior. One third of the tumors arise in the adrenal gland, one third in the retroperitoneum, and the remaining one third in the posterior mediastinum, with only rare manifestations in the neck or pelvis [12].

Ganglioneuromas are the most mature neural crest tumors and are histologically benign. One third of the cases are located in the retroperitoneum, and only rarely do they arise in the adrenal gland. Ganglioneuromas occur in older children, can be completely asymptomatic, and are often incidental findings on US or chest radiographs. When they invade the spine, neurologic symptoms can occur related to cord compression. Ganglioneuroblastomas and Ganglioneuromas cannot be distinguished from neuroblastoma with imaging alone, and therefore there is no standard imaging protocol for follow-up [12].

Pheochromocytoma is an uncommon pediatric neoplasm. It accounts for less than 1 % of all tumors seen in pediatric centers and is rarely diagnosed in infancy with the mean age at diagnosis being 11 years in children [20]. In the pediatric age group, 80 % of pheochromocytomas occur in the adrenal gland with bilateral involvement in 25 % [20, 21]. In the 20 % of extra-adrenal cases, the most frequent site is the upper abdomen [22]. Less common extra-adrenal sites include the sympathetic chain in a cervical, thoracic, or pelvic location, and, in rare cases, they may occur in the urinary bladder , spinal cord, and vagina. When occurring outside the adrenal gland, the tumors are usually referred to as paragangliomas. Multiple tumors are present in 30–70 % of the patients, especially in those with a positive family history for pheochromocytoma and in association with multiple endocrine neoplasia (MEN) type II, neurofibromatosis 1, or von Hippel–Lindau disease. In addition to age at presentation, the clinical presentation also differs from neuroblastoma, as pheochromocytoma arises from the chromaffin cells of the medulla that are actively producing epinephrine and norepinephrine and occasionally vasoactive intestinal peptide (VIP). The first-line imaging modality is US, on which pheochromocytoma may present as a homogeneous soft tissue mass measuring 2–5 cm on average, but it may also contain heterogeneous areas, caused by hemorrhage, necrosis, or calcifications (Fig. 14.3) [7]. The tumor is often well encapsulated and color Doppler examination reveals hypervascularization [23]. MIBG scanning is more sensitive than US and can be positive, even when US shows no abnormalities [17].