Fig. 2

Immunohistochemistry of the level of S100A10 expression in case 1. a Aggregates of tumor buds and PDCs are found mainly in the left image (surrounded by arrows). Hematoxylin and eosin stain. Scale bar: 200 μm. b Image corresponds to (a). Positive reactions are noted not only in both tumor buds and PDCs (surrounded by arrows) but also in the tumor cells protruding into the stroma. By contrast, the glandular components (asterisks) with a smooth border around the stroma show no or weak cytoplasmic positivity, except for a reaction at their luminal surface. S100A10 immunostain. Scale bar: 200 μm. c Magnified image of (b). Positive reactions in the protruding tumor cells are indicated by arrowheads, and the smooth border of glandular components is indicated by asterisks. S100A10 immunostain. Scale bar: 100 μm. d Image corresponds to (c). Cord-like or small nest appearance of the protruding tumor cells (arrowheads) is more visible with pan-cytokeratin immunostain. AE1/AE3 immunostain. Scale bar: 100 μm