Figure 1
From: Congenital hyperinsulinism: current trends in diagnosis and therapy
Histology of the focal form of HI. Histological features of focal form (A1-A4) on frozen sections stained by toluidine blue (A1, A3, A4) and on immunostaining with proinsuline antibody (A2). At low magnification (A1, x25; A2, x16) a modified architecture of pancreatic tissue is observed within the focal form. The focal form is not encapsulated and is poorly delimited. It contains focal adenomatous hyperplasia of islets (pale areas) intermingled and/or surrounded by exocrine acini (darkest area underlined by white stars) (A1 and A3). This pattern is underlined by proinsuline showing an evident contrast between the focal lesion and normal pancreas (doted line circles). At high magnification (A3 and A4, × 200), the focal lesion (A3) is composed of islets containing a heterogeneous population of endocrine cells of various sizes. Some of these cells have large nuclei (arrows, A3) and large cytoplasms. By contrast, normal islets (doted line circles) observed outside the lesion have endocrine cells of usual size without enlarged nuclei (A4).