Fig. 1: Pseudo-IPMNs characterized by cysts showing papillary and mucinous linings.

A Invasive carcinoma invading to a secondary (retention) cyst is forming a compact papillary nodule virtually indistinguishable from an IPMN. B This retention cyst is lined partially by normal ductal epithelium (left), and partially by invasive carcinoma colonizing the surface (cancerization, right) mimicking IPMN (H&E stain). Invasive carcinoma is typically seen on the wall of these cysts (lower left in (A), and middle-lower in (B)).