Expression of proinsulin and insulin in insulinoma and normal pancreas

Objective To investigate the expression of proinsulin, insulin, C-peptide in insulinoma and normal pancreas and their roles. Methods Thirty-eight cases of insulinoma and 20 cases of normal pancreas from Sep. 2006 to Dec. 2009 in our hospital were selected. Immunohistochemistry was used to determine the expression of proinsulin, insulin, C-peptide. Results Proinsulin, insulin, C-peptide was expressed in insulinoma and normal pancreas. Proinsulin, C-peptide were strongly expressed in 100%insulinoma, while they were weekly expressed in 55% ～60% normal pancreas; insulin was expressed as + + +in 79% insulinoma, while it was expressed as + + + + in 85% normal pancreas. Proinsulin, C-peptide positive cell accounted for 80% ～ 100% of 38 insulinoma, and insulin positive cell accounted for 50% ～ 70%,the proinsulin/insulin ratio ＞ 1 accounted for 78.9%; while the corresponding values were 20% ～ 80%, 60% ～90%, 10.0% in normal pancreas, and the difference was statistically significant ( P ＜ 0.05 ). Conclusions The proinsulin/insulin ratio ＞ 1 is 78.9% in insulinoma, and detection of proinsulin may help to diagnose insulinoma. Key words: Pancreas;  Insulinoma;  Insulin;  Proinsulin;  C-peptide;  Immunohistochemistry