We determined protein expression of ARX and PDX1 together with ATRX, DAXX, ARID1A, and H3K36me3 by immunohistochemistry, as well as ALT and CDKN2A deletions by fluorescence in situ hybridization (FISH), in a cohort of clinically defined sporadic insulinomas. The gene discussed is ATRX; the disease is pancreatic insulinoma.