Sections demonstrate a large diverticulum lined by small intestinal mucosa .
Focally, ectopic gastric mucosa is identified in the tip of the diverticulum. Beneath the mucosa, in the wall of the diverticulum, there are nodules of basophilic cells . At higher magnification, these cells are forming nests and cords . There is a moderate amount of amphophilic cytoplasm. Chromogranin stain is positive in these cells.