INS and neoplasm: Despite decreases in insulin secretion, some studies have reported post-pancreatectomy improvements in glucose control in malignant cases.27,28 Because malignant pancreatic tumors are known to produce substances that impair the action of insulin and decrease insulin sensitivity, a patient’s diabetic status can sometimes improve after tumor removal.29,30 Of the nine patients in our study who showed stable glycemic control (eight with HbA1c ≤ 0.1 %) or improved control (one with HbA1c reduced by 0.4 %) during the post-DP follow-up period, five had malignant tumors.