Therefore, in an effort to devise a tool that could be adapted for daily clinical practice, a classification based on surrogate markers was developed, consisting of the following groups: POLE, which includes tumors with mutations in the exonuclease domain of the POLE gene; mismatch repair deficiency (MMRd), for tumors with loss of expression of mismatch repair pathway proteins; p53 abnormal, for tumors with altered p53 expression; and non-specific molecular profile, for the remaining tumors, which do not exhibit a specific molecular alteration (9). The gene discussed is POLE; the disease is hyperinsulinemic hypoglycemia, familial, 4.