Molecular and immunohistochemical analyses of the focal form of congenital hyperinsulinism

• Published in: Modern pathology Vol. 19; no. 1; pp. 122 - 129
• Main Authors: Suchi, Mariko, MacMullen, Courtney M, Thornton, Paul S, Adzick, N Scott, Ganguly, Arupa, Ruchelli, Eduardo D, Stanley, Charles A
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.01.2006; Elsevier Limited
• Subjects: adenomatous hyperplasia; Adenosine Triphosphate - metabolism; ATP-Binding Cassette Transporters - genetics; ATP-sensitive potassium channel; Cell cycle; Cell growth; Chromosomes, Human, Pair 11 - genetics; congenital hyperinsulinism; Congenital Hyperinsulinism - genetics; Congenital Hyperinsulinism - metabolism; Congenital Hyperinsulinism - surgery; Cyclin-Dependent Kinase Inhibitor p57 - biosynthesis; Cyclin-dependent kinases; Dehydrogenases; Endocrinology; Haplotypes - genetics; Hospitals; Humans; Hyperplasia; Immunohistochemistry; Infant; Infant, Newborn; Insulin; Kinases; loss of heterozygosity; Medicine; Microsatellite Repeats - genetics; Mutation; nesidioblastosis; p57kip2; Pancreas; Pancreas - metabolism; Pancreas - pathology; Pancreas - surgery; Pancreatectomy; Pathology; Potassium; Potassium Channels - genetics; Potassium Channels - metabolism; Potassium Channels, Inwardly Rectifying - genetics; Receptors, Drug - genetics; Sulfonylurea Receptors; United States > US; Wisconsin; nesidioblastosis; adenomatous hyperplasia; congenital hyperinsulinism; loss of heterozygosity; p57kip2; ATP-sensitive potassium channel
• ISSN: 0893-3952; 1530-0285
• DOI: 10.1038/modpathol.3800497

Congenital hyperinsulinism is a rare pancreatic endocrine cell disorder that has been categorized histologically into diffuse and focal forms. In focal hyperinsulinism, the pancreas contains a focus of endocrine cell adenomatous hyperplasia, and the patients have been reported to possess paternally inherited mutations of the ABCC8 and KCNJ11 genes, which encode subunits of an ATP-sensitive potassium channel (KATP). In addition, the hyperplastic endocrine cells show loss of maternal 11p15, where imprinted genes such as p57kip2 reside. In order to evaluate whether all cases of focal hyperinsulinism are caused by this mechanism, 56 pancreatectomy specimens with focal hyperinsulinism were tested for the loss of maternal allele by two methods: immunohistochemistry for p57kip2 (n=56) and microsatellite marker analysis (n=27). Additionally, 49 patients were analyzed for KATP mutations. Out of 56 focal lesions, 48 demonstrated clear loss of p57kip2 expression by immunohistochemistry. The other eight lesions similarly showed no nuclear labeling, but the available tissue was not ideal for definitive interpretation. Five of these eight patients had paternal KATP mutations, of which four demonstrated loss of maternal 11p15 within the lesion by microsatellite marker analysis. All of the other three without a paternal KATP mutation showed loss of maternal 11p15. KATP mutation analysis identified 32/49 cases with paternal mutations. There were seven patients with nonmaternal mutations whose paternal DNA material was not available, and one patient with a mutation that was not present in either parent's DNA. These eight patients showed either loss of p57kip2 expression or loss of maternal 11p15 region by microsatellite marker analysis, as did the remaining nine patients with no identifiable KATP coding region mutations. The combined results from the immunohistochemical and molecular methods indicate that maternal 11p15 loss together with paternal KATP mutation is the predominant causative mechanism of focal hyperinsulinism.