LOSS OF HETEROZYGOSITY ON THE SHORT ARM OF CHROMOSOME-1 AND CHROMOSOME-3 IN SPORADIC PHEOCHROMOCYTOMA AND EXTRAADRENAL PARAGANGLIOMA

Pheochromocytomas and extra-adrenal paragangliomas are tumors of the p araganglia with similar histological characteristics. We examined 12 s poradic pheochromocytomas and 5 extra-adrenal paragangliomas for loss of heterozygosity (LOH) in chromosomes 1p and 3p using a microdissecti on technique. Chromosomes 1p34-36, 3p21 and the von Hippel-Lindau (VHL ) gene locus (3p25) were analyzed. LOH of a selected region on chromos ome 1p was detected in 5 of 11 (45%) informative pheochromocytoma case s and in 0 of 5 (0%) informative extra-adrenal paraganglioma cases, LO H of the chromosome 3p25 VHL gene locus was detected in 5 of 9 (45%) i nformative pheochromocytoma cases and in 0 of 3 (0%) informative extra -adrenal paraganglioma cases. LOH of 3p21 was detected in 2 of 4 (50%) informative extra-adrenal paraganglioma cases. The allelic deletions in chromosomes 1p and 3p appear to be separate events. In conclusion, significant deletions were found at 1p34-36 and 3p25 in sporadic pheoc hromocytomas but not in extra-adrenal paragangliomas. These findings s uggest (1) that multiple genetic factors may be involved in pheochromo cytoma tumorigenesis, and (2) extra-adrenal paragangliomas may have a different genetic mechanism of tumorigenesis compared with pheochromoc ytomas.