Silent advanced large cell neuroendocrine carcinoma with synchronous adenocarcinoma of the colon: A case report

Figure 3 Histologic and immunohistochemical findings of colonic large cell neuroendocrine carcinoma. Histologic findings of colonic adenocarcinoma. Immunohistochemical stain for CK20 in both colonic large cell neuroendocrine carcinoma and colonic adenocarcinoma. A: Low power view of biopsy specimen reveals several tissue fragments mainly consisted of tumor (black arrows), ulcer debris (white arrow), and non-neoplastic colonic mucosa (arrowhead) (HE, × 20); B: Medium power view displays invasive tumor cells forming organoid structures such as cords or small nests (HE, × 100). Tumor cells display severe atypia and have round nuclei, sometimes with prominent nucleoli (arrows), and moderate amounts of cytoplasm, with high mitotic rate (Inset, HE, × 400); C: Infiltrating tumor cells are identified by immunohistochemical stain for cytokeratin (CK, × 100). Note the non-neoplastic mucosal glands (arrows) that are separated from the tumor; D: Tumor cells show strong immunoreactivity for neuroendocrine marker (synaptophysin, × 100). Note the non-neoplastic mucosal glands (arrows) are negative for neuroendocrine marker; E: Low power view of biopsy specimen reveals colonic epithelial proliferative lesion forming tubular and papillary structures (HE, × 20); F: Medium power view displays invasive growth of tumor cells that form irregular branching and budding of glands (HE, × 100); G: Infiltrating tumor cells of colonic large cell neuroendocrine carcinoma are immunoreactive for CK20 (× 100); H: Invasive tumor glands of colonic adenocarcinoma are also immunoreactive for CK20 (× 100).