MIBG Case 4 Answers

1) Any abnormal uptake?

Two areas of abnormal uptake are noted. One lies in the midline in the low abdomen, the other is a faint region to the left of the mid-mediastinum. On CT the mediastinal lesion had been overlooked initially and the midline abdominal lesion was arising de novo in the organ of Zuckerkandl.

2) Is this a recognized syndrome?

Yes, familial phaeochromocytomas and paragangliomas is a recognized very rare syndrome. Isolated familial phaeochromocytoma is genetically very similar to von-Hippel Lindau syndrome and thought to be a poorly penetrate variant of this. Phaeochromocytomas are also associated with Neurofibromatosis type 1, MEN 2, von Hippel-Lindau syndrome and Carney's syndrome.

3) What percentage of phaeochromocytomas are extra-adrenal in adults?

Phaeos obey the rule of 10s. 10% are extraadrenal, 10% are malignant, 10% occur in the paediatric population, 10% are multiple, 10% are familial and 10% are cystic.

The larger the tumour, the more malignant it tends to be. Children tend to have multiple, extra-adrenal tumours that are more malignant. Extra-adrenal tumours generally arise in the retroperitoneal sympathetic chain or near the organ of Zuckerkandl (caudal to the original of the IMA). Mediastinal phaeos make up ~1% of all phaeos. In adults, extra-adrenal lesions are malignant in 30-40% of cases whereas this is not true in children.

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