[Scintigraphy using I 131 iodobenzylguanidine and malignant melanomas]

The successful use of iodine-131-meta-iodobenzylguanidine (I-131-MIBG) scintigraphy for diagnosis of phaeochromocytoma and neuroblastoma stimulated investigation into its diagnostic and therapeutic usefulness in other neural crest tumours. It appears that there is a difference in capacity to absorb I-131-MIBG between the different tumour types. In I-131-MIBG scintigraphy of carcinoids there are more false negative results in comparison with phaeochromocytomas and neuroblastomas. Melanoma, also a neural crest tumor, turned out to be false negative in 100% of the cases reported until 1989. The authors present a case of a malignant melanoma with metastases in liver and stomach, concentrating I-131-MIBG. Biochemical examination demonstrated that this particular tumour was metabolically very active. It is suggested that the I-131-MIBG-positive scintigram of the melanoma may be related to the level of metabolic activity. By biochemical screening in proven cases of malignant melanoma it may be possible to select cases in which I-131-MIBG scintigraphy is worthwhile with a view to therapeutic application of I-131-MIBG.