Fig. 4

a The 60 × 50 mm multilobular cystic lesion was observed in the pancreatic head. The cut surface of the resected specimen in the pancreas head showed a large multilobular cystic mass filled with mucin and mural nodules. The partition wall of the mass was exceedingly hard, demonstrating calcification (black arrow). The precise area of the carcinoma component was described using the red dotted line annotation method. b Tumor cells were composed of tall papillae lined by columnar cells with pseudostratified nuclei and basophilic cytoplasm with variable amounts of apical mucin. Hematoxylin and eosin staining, ×50. c Calcification was observed on a part of the wall forming the mucin pools (black arrow). Infiltration of inflammatory cells into part of the wall forming the mucin pools was also observed (black arrowheads). Hematoxylin and eosin staining, ×50