Comparison

The percentage uptake of [123l]metaiodobenzylguanidine (MIBG) by tumors of the paraganglion system is compared with the number of neurosecretory granules (assessed by both light and electron microscopy) in the subsequently resected tumors in six patients. lodine-123 MIBG was injected intravenously; the tumor uptake of [123I]MIBG varied between 0.001 % and 0.14 % of the injected dose per gram of tumor tissue at 22 hr. The number of neurosecretory granules in tissue sections was scored on a scale of l-lll. A direct proportional correlation was found between the percentage uptake of [123I]MIBG by the tumor and the number of neurosecretory granules in the tissue sections but not with plasma or urinary catecholamines. This technique for imaging reflects the storage status of the tumor better than plasma and urinary catecholamine measurements. J NucÃ-Med 28:973-978,1987 he paraganglion system comprises collections of neuroepithelial cells scattered throughout the body. The definitive common feature of these cells is the presence of numerous neurosecretory granules containing cate cholamines in their cytoplasm (7). Paragangliomas are the better differentiated tumors arising from this system and their cells contain numerous catecholamine gran ules. Pheochromocytomas are paragangliomas of the adrenal medulla. Neuroblastomas and ganglioneuro-blastomas are poorly differentiated tumors believed to arise from precursors of this system, and these two tumors contain fewer cytoplasmic catecholamine gran ules. Neurosecretory granules containing catecholamines have the ability to fix chrome salts and have been described as chromaffin if this property is easily demon strable and nonchromaffin if it is not. However, chro-maffinicity depends very much on type and pH of fixation, does not correspond specifically to adrenalin