Fig. 1Colonoscopic finding showed a large fungating mass that interrupts the lumen of the ascending colon.
Fig. 2Contrast-enhanced computed tomography showed invagination of the terminal ileum into the ascending colon with an approximately 3 cm mass (A; arrow) and irregularly shaped multiple mesenteric lymph nodes with central low density (B; arrow).
Fig. 3Gross findings revealed a polypoid and ulceroinfiltrative mass measuring 8.0 cm × 5.5 cm in the cecum.
Fig. 4(A) Hematoxylin and eosin stained sample at ×40 magnification demonstrated sheets of monomorphic large cells with large round nuclei and abundant cytoplasm (inside the yellow line) and islands of tumor cells with glandular structures (inside the blue line). Hematoxylin and eosin stained tissue at ×200 magnification was consistent with a poorly differentiated adenocarcinoma (B) and a neuroendocrine carcinoma (C).
Fig. 5(A) The tumor cells revealed a positive and diffuse reaction. Immunohistochemical staining for synaptophysin (×200). (B) The tumor cell revealed a positive reaction in the neuroendocrine differentiation area. Immunohistochemical staining for chromogranin (×200).