Ampullary neuroendocrine tumor diagnosed by endoscopic papillectomy in previously confirmed ampullary adenoma

Figure 3 The protruding whitish mass lesion (second papillectomy tissue, Figure 2D) was composed of two lesions that differed in their histological characteristics. Tubular adenoma (solid arrow) and NET [Dotted arrow, hematoxylin-eosin (HE) staining, magnification × 4; A]. The tubular adenoma lesion exhibited round-to-oval enlarged glands with stratified epithelial cells (HE staining, magnification × 100; B). The NET showed cord-like arrangement of monotonous tumor cells (HE staining, magnification × 100; C). Immunohistochemistry showed that the tumor cells were positive for synaptophysin (magnification × 100; D).