Morphology

 Early stage of acute appendicitis  

Scant neutrophilic exudate throughout the mucosa, submucosa and muscularis propria. Subserosal vessels will become congested and often with perivascular neutrophilic infiltrate. The inflammation transforms the normal glisterning serosa into a dull, granular and red.

Late acute appendicitis 

Dense neutrophils infiltration and fibropurulent serosal exudates over the serosa.Abscess formation with ulceration and suppurative necrosis occur within the wall. Subsequently, acute gangrenous necrosis will occur if there is green-black gangrenous necrosis through the wall extending to the serosa and immediately followed by appendix rupture.

Picture (a) and (b) shows acute appendicitis with neutrophils infiltration throughout mucosa, submucosa and muscalaris layers at different magnification.

Picture above shows the enlargement of appendix and  red inflamed mucosa with an irregular luminal surface.