Coexistence of small cell neuroendocrine carcinoma and villous adenoma in the ampulla of Vater

Figure 3 Histopathological findings. A: The tumor cells are composed predominantly of small to medium-sized, round or oval cells with hyperchromatic nuclei, inconspicuous nucleoli and scanty cytoplasm (HE, × 400); Immunohistochemically, the tumor cells are positive for synaptophysin (B) and low-molecular-weight cytokeratin (C) (× 200); D: Light microscopy shows the coexistence of villous adenoma and small cell neuroendocrine carcinoma (HE, × 20); E: The epithelium of the adenoma (long arrows) is in continuity with the small cell neuroendocrine carcinoma (short arrows) (HE, × 200).