Fig. 3

Postoperative pathology findings: a On gross examination, the cystic lesion (measuring 1.0 × 0.5 × 0.4 cm) had a thick wall, and the cyst wall partially protruded into the lumen (enlarged view, arrowhead). b, c Hematoxylin and eosin staining showed that the cyst wall was lined with monolayer columnar epithelium without atypia, and the stroma was composed mainly of short spindle cells along with some blood vessels and smooth muscle cells (B × 40, C × 200). d There were several microcysts within the cyst wall, some of which were dilated and protruded into the interior of the cyst (The cyst wall is indicated by small arrows and the dilated microcyst by large arrows). Some of these would have been visible as intracavitary nodules on CT (× 20). e The cells lining the cystic spaces were positive for TTF-1 (× 100). f The cells in the stroma were positive for vimentin (× 100)