Nuclear Oncology by Aktolun Cumali & Goldsmith Stanley

Author:Aktolun, Cumali & Goldsmith, Stanley
Language: eng
Format: epub
ISBN: 978-1-4698-8349-6
Publisher: LWW
Published: 2014-09-03T16:00:00+00:00

The clinical signs and symptoms depend on the size of the primary tumor, effect of hormone production, and the location of distant metastases. It may be found incidentally without any symptoms or present with abdominal pain and mass, generalized bone pain, anemia, malaise, fever, irritability, weight loss, encephalitic symptoms and even blindness, and paraneoplastic syndrome.

Because metastases are common at presentation, accurate staging depend on multimodality imaging. Initial imaging in children with NB is usually performed to confirm the diagnosis and investigate the presenting symptoms. Chest x-ray, abdominal radiographs, skeletal films, abdominal ultrasound or computerized tomography, spinal MRI (in cases of paraspinal NB), MIBG scintigraphy, and probably bone scan are among the investigations depending on the clinical findings.

Ultrasonography (US) is the initial imaging modality for the evaluation of abdominal mass in a child. It is useful for the diagnosis of abdominal mass, and the evaluation of local extent of the primary tumor. On US, NBs are heterogeneous solid lesions, mostly echogenic, with calcification and less commonly with cystic anechoic areas. CT scan shows lobulated nonuniform masses with heterogeneous or little enhancement. Calcifications, pseudonecrosis or hemorrhage may also be seen. Both CT and MRI are useful for assessment of the location and the size of the primary tumor, vascular encasement, tumor respectability, and retrocrural and paravertebral extension.49

MRI is superior to CT to assess bone marrow infiltration and intraspinal extension of tumor. Moreover, the lack of ionizing radiation and the absent necessity of using oral contrast are other advantages of MRI.49 On MRI, the tumor is typically heterogeneous with a variable enhancement pattern, prolonged T1 and T2 relaxation times with low signal intensity on T1W and high signal intensity on T2W images. Epidural invasion of NB and leptomeningeal involvement should be assessed with MRI on any patient with paraspinal NB.40,50

Bone metastasis is relatively common in NB. Detection of bone metastasis is important for staging (stage IV). Whole-body bone scan with 99mTc-MDP has been widely used in NB to evaluate bone metastasis. Bone metastases are usually present with focal increased uptake in the skeleton. However, cold defects and asymmetric metaphyseal increased activity may also reveal bone metastases. In children, detection of bone metastasis near the epiphysis is difficult. Even with a slightly blurring of the growth plate margins, bone metastasis should be ruled out.51 Involvement of the skull and facial bone including periorbital regions may be also seen with more advanced bone metastases. The sensitivity of MIBG to detect bone metastases is higher than bone scan (Fig. 25.4).52 Moreover, the specificity of the positive lesions in bone scan is lower than MIBG scintigraphy. However, there are some instances of positive bone scans with negative MIBG studies.53,54 Thus, bone scan is still needed for accurate staging at diagnosis. Omitting bone scanning in the diagnostic staging may lead to incorrect staging up to 10% of cases.55 On the contrary, in a clinically responding patient, bone scan is not recommended in the routine follow-up studies unless MIBG scan is not available, or with a negative MIBG scan and suspicious radiographic findings.

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