Figure 2

Histology of the diffuse form of HI. Histological features of diffuse form (B1- B4) on frozen sections stained by toluidine blue (B1, B3) or on formalin fixed paraffin embedded section stained with HES (B4) or with proinsuline antibody (B2). At low magnification (B1, x25; B2, x16), the architecture is preserved with a normal distribution between exocrine (dark) and endocrine area (pale). At higher magnification (B3 and B4 x200), abnormal endocrine islets contain cells with voluminous nuclei (arrows, B3) and enlarged cytoplasm. The entire pancreas is interspersed with abnormal islets intermingled with morphologically normal islets in a variable proportion (B4). To confirm a diffuse form on extemporaneous frozen sections, abnormal islets must be observed on biopsies sampled from at least 2 or 3 distinct areas of the pancreas.