| Background and objective:Insulinomas are the most common pancreatic neuroendocrine neoplasmas. Most of insulinomas are single and benign, only 10% are malignant. In the presence of an insulinoma, the semiautonomous basal insulin secretion inhibits hepatic glucose efflux,leading to fasting hypoglycemia.Severe hypoglycemia can lead to degenerative changes in the cerebral cortex and atrophy, resulting in irreversible damage nerve tissue.So it is important to detect and to find the cause of hypoglycemia early,at the same time it is necessary to resect the tumor completely.We misdiagnosed 14 insulinomas,33% of the IRI/G value were equal to or less than 0.3,without detecting plasma proinsulin in our hospital.We detect true insulin except plasma proinsulin by microparticle enzyme immunoassay.Early studies have shown that proinsulin/insulin is high in 85-100% insulinoma patients,so we confirm the increased content of proinsulin in insulinoma from the tissue level.Method:The clinical characteristics of 38 insulinomas and 20 normal pancreas tissue confirmed by pathology analyze in our hospital from September 2006 to December 2009 were retrospectively analyzed. The diagnosis of insulinoma is referred to the criteria used by Yang et. Immunohistochemistry (SP method) was used to study the expression of proinsulin,insulin, C-peptide in insulinoma and normal pancreas.Results:In 38 cases of insulinoma patients,16 males(42.1%)and 22 females(57.9%).The age ranged from 11 years to 74 years,with the average of (41.7±14.47)years,among which males (43.9±13)years, females (39.5±16.6)years.The period from onset to diagnosis ranged from 15 days to 1970 days,with the average of 495.14±672.87 days.All the tumors are single and benign.The diameters ranged from 0.5cm to 3.0cm,with the average of 1.783±0.80cm,60.52% of which were eque to or less than 2cm.The number of tumors is 38.8 tumors located in the pancreatic head(21.05%),24 tumors pancreatic body and tail(63.16%),6 tumor uncinate process(15.79%). Insulin, proinsulin and C-peptide were stained in the same insulinoma tissue and the same normal pancreas for different sections.It displayed that the average positive cell of insulin is (39.39±10.15)%,which is lower than in normal pancreas (49.50±16.63) %, P=0.019 was considered significant; the average positive cell of proinsulin is (55.97±9.79)%,which is higher than in normal pancreas(46.25±15.72)%;P=0.021 was considered significant; the average positive cell of C-peptide is (55.89±8.95) %,which is higher than in normal pancreas(44.50±17.36)%,P=0.013 was considered significant; the average number of proinsulin/insulin is 1.36±0.33,which is higher than in normal pancreas (0.78±0.21), P=0.000 was considered significant; The proinsulin/insulin ratio is above one in 30 insulinomas,ranged from 1.06 to 1.188,left the remained 8 cases below one.The ratio of proinsulin/insulin is below one in 18 normal pancreas,ranged from 0.84 to 0.94,left the other two cases above one,χ2=25.186,P<0.05 was considered significant.The plasma insulin was measured in 28 cases insulinoma of 38 cases,of which the value is low or normal in 10 cases,ranged from 1.8 to 6.9mIU/L,the average of the plasma insulin value is 4.10±1.807 mIU/L,the ratio of proinsulin/insulin is above one in 8 cases of its corresponding insulinoma tissue,while the other 2 cases is below one.The plasma insulin is high in the remained 18 cases,14 cases of which the ratio of proinsulin/insulin is above one,4 cases below one.Conclusion:1. The proinsulin and C-peptide levels in patients with insulinoma were significantly higher than those in normal pancreas, while the insulin levels were significantly lower than those in normal pancreas.2. The proinsulin/insulin ratio is above one in most insulinoma, coninciding with the level in plasma, which indicated that the plasma insulin can't be a criteria to exclude the diagnosis of insulinoma that plasma insulin concentration is normal or below normal.It may help to diagnose insulinoma by clinical manifestations and the plasma proinsulin level. |
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