Acquired Conditions

Published on 27/02/2015 by admin

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Last modified 27/02/2015

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Chapter 123

Acquired Conditions

Neuroblastoma

Overview: Neuroblastoma is the most common extracranial solid neoplasm in children and accounts for almost 10% of all childhood neoplasms.1 Neuroblastoma arises in the abdomen in two thirds of cases; of these, about two thirds of lesions occur in the adrenal, whereas the remainder may arise anywhere along the sympathetic nerve chains.1

Neuroblastoma, ganglioneuroblastoma, and ganglioneuroma belong to a group of related neoplasms arising from neural crest tissue that are distinguished by their degree of cellular maturation and differentiation. Neuroblastoma accounts for the vast majority of these lesions and has the most primitive and malignant cells.2 Ganglioneuroma represents the more differentiated end of the spectrum and is benign. Ganglioneuroblastomas represent an intermediate group with mixed histology.

Most children with neuroblastoma present between 1 and 5 years of age, with a median age of almost 2 years.2 Neuroblastoma is more common in patients with neurofibromatosis type 1, Beckwith-Wiedemann syndrome, Hirschsprung disease, central hypoventilation syndrome, and DiGeorge syndrome.2

Neuroblastomas typically present as palpable masses or with symptoms and signs related to local tumor invasion, metastatic disease, and the effects of hormone production or autoimmune response (opsoclonus-myoclonus syndrome). Metastatic disease is seen in up to 70% of patients at presentation.3 The most common sites include local and distant lymph nodes, bone, bone marrow, liver, and skin.

The diagnosis of neuroblastoma can be made by tissue biopsy, but a combination of positive bone marrow aspirate and increased urinary catecholamine metabolites (vanillylmandelic acid and homovanillic acid) is sufficient to confirm the diagnosis. The urinary level of catecholamine metabolites is increased in almost 90% of cases of neuroblastoma.4 The International Neuroblastoma Staging System has been the most commonly used worldwide for staging neuroblastoma.1,2,4 However, its application has encountered many difficulties, as it relies on the extent of tumor resected at surgery. For this reason, a new staging system, the International Neuroblastoma Risk Group Staging System, was developed in 2009, and this system relies on preoperative imaging findings (imaging risk factors) and detection of metastatic disease (Box 123-1).5

The prognosis of neuroblastoma depends on stage at presentation, patient’s age (children younger than 12 to 18 months have better prognosis), histologic category, grade of tumor differentiation, status of the MYCN oncogene, chromosome 11q status, and deoxyribonucleic acid ploidy.6

Imaging: Adrenal neuroblastomas and those arising from the adjacent retroperitoneal area are usually easily identified with ultrasonography, computed tomography (CT), or magnetic resonance imaging (MRI) because the mass is generally quite large by the time of presentation (Fig. 123-1). Very small masses are uncommon, and in those cases seen beyond the neonatal age, CT and MRI play a more important role than ultrasonography (Fig. 123-2). On ultrasonography, the masses have a variety of appearances with the most characteristic being that of a solid, heterogeneous, hyperechoic mass, often with small hyperechoic foci with or without acoustic shadowing caused by calcification (e-Fig. 123-3).1,2,4 Anechoic areas resulting from cystic, hemorrhagic, or necrotic changes may be present (e-Fig. 123-4).

The new International Neuroblastoma Risk Group Staging System requires the use of CT, MRI, or both for staging.5 On CT, neuroblastomas usually show heterogeneous enhancement, depicting solid areas along with areas of necrosis, hemorrhage, and cystic change (see Fig. 123-1). Calcification is present in more than 90% of cases (see Figs. 123-1, 123-2, and e-Figs 123-3 and 123-4).4 On MRI, the lesions are usually heterogeneous, with predominantly low signal on T1-weighted images and high signal on T2-weighted images, and with variable degrees of enhancement (Fig. 123-5).2,4

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