GNAS and cancer: While evidence for events on a smaller scale involving imprinted genes in cancer is limited, small germline microdeletions, microinsertions, and chromosomal rearrangements have been reported within the GNAS locus and in the genes adjacent to GNAS at 20q13, in patients with endocrine disorders pseudohypoparathyroidism type 1a and type 1b [174, 175].