“…Using tumor imaging studies in combination with the hypergastrinemia to diagnose ZES, as is increasingly being done in recently reported cases [82, 84, 87, 88, 90, 94, 110, 134] with patients taking or not taking PPIs, has other limitations. In the presence of PPI therapy, one cannot exclude the presence of appropriate hypergastrinemia if a tumor is seen on cross-sectional imaging studies (CT, ultrasound, or MRI), whether the patient has MEN1 syndrome or not and the mass itself may not even be a NET.…”