Fig. 1: Gross and histologic features of mucinous neoplasms and non-neoplastic appendices.

Mucinous neoplasms frequently cause fusiform enlargement of the appendix due to accumulation of thick tenacious mucus (a). Non-neoplastic appendices show minimal dilatation with preserved layers of the wall and small cysts (arrows) representing diverticula (b). Mucinous neoplasms display circumferential involvement of the lumen (c) with obliterated tissue planes between the layers of the appendiceal wall (d). Ruptured diverticula feature focal disruption of an otherwise normal muscularis propria (e). The muscularis mucosae is of near normal thickness and is clearly separated from the submucosa (f).