Why is identifying ganglion cells important?

Ganglion cells are absent in Hirschsprung disease (also called aganglionic megacolon).

Anatomy:
There are two neural plexus in the intestine - Submucosal (Meissner's) and myenteric (Auerbach's).

Submucosal (Meissner's) plexus - Present just beneath the muscularis mucosa.

In figure, red arrow --> Muscularis mucosa, blue arrow --> muscularis propria.
Space between the two (green line) --> submucosa; Yellow circle --> Submucosal plexus of ganglion cells.


Myenteric (Auerbach's) plexus - Present inbetween the two muscular layers of the bowel wall.

In figure, arrow --> neuronal processes
Circle --> Ganglion cell clusters

Important points:

• Ganglion cells are often associated with neuronal processes and Schwann cells.
• These interconnect and create a neural network throughout the submucosal  layer. 

• Often occur in clusters and may mimic giant cells, epithelioid cells or granulomas.

                               In figure, arrow --> neuronal processes, circle --> ganglion cells.

Diagnosis of Hirschsprung disease:
Absence of ganglion cells in the submucosal and the myenteric plexus.

Other features in favour of Hirschsprung's disease:
Hypertrophy of nerve bundles.
Hypertrophy of muscularis mucosae.