Immunostaining for Hu C/D and CD56 is useful for a definitive histopathological diagnosis of congenital and acquired isolated hypoganglionosis.

Isolated hypoganglionosis (IHG) has been proposed as a distinct entity with two subtypes: congenital IHG (CIHG) and acquired IHG (AIHG). However, due to the rarity of the disease and the lack of defining histological criteria, the concept of IHG is not widely accepted. We studied paraffin-embedded intestinal specimens from 79 patients diagnosed with Hirschsprung's disease (HD) (n = 49), CIHG (n = 25), and AIHG (n = 5) collected between January 1996 and December 2015. Histopathological diagnosis of HD, CIHG, and AIHG was confirmed by hematoxylin and eosin staining and immunohistochemical staining using Hu C/D and CD56. We evaluated (immuno)histopathological findings, counted the number of ganglion cells, and measured the size of Auerbach's plexus. Hu C/D labeled neuronal cell bodies, whereas CD56 was detected in all neuronal components. In HD, all ganglion cells in Auerbach's plexus in the normoganglionic segment (NGS) were immunoreactive for Hu C/D, whereas in the aganglionic segment (AGS), these were replaced by CD56-positive extrinsic nerve fibers and bundles. The number of ganglion cells in AIHG and CIHG was significantly lower than in the NGS of HD (p < 0.05). Auerbach's plexus was significantly smaller in CIHG (p < 0.05) but in AIHG equivalent to the NGS in HD. In summary, immunostaining for Hu C/D and CD56 is useful for definitive histopathological diagnosis of IHG.