Collision carcinoma of the rectum involving neuroendocrine carcinoma and adenocarcinoma: A case report

Figure 4 Immunohistochemical staining of cytokeratin, chromogranin A, synaptophysin, and CD56, β-Catenin and CK20. A: Adenocarcinoma cells were strongly positive for cytokeratin (CK), while neuroendocrine carcinoma cells were weakly positive [immunohistochemistry (IHC) 200 ×]; B: Adenocarcinoma cells were negative for chromogranin A, while neuroendocrine carcinoma cells were positive (IHC 100 ×); C: Adenocarcinoma cells were negative for synaptophysin, while neuroendocrine carcinoma cells were positive (IHC 200 ×); D: Adenocarcinoma cells were negative for CD56, while neuroendocrine carcinoma cells were positive (IHC 200 ×); E: Adenocarcinoma cells were strongly positive for β-Catenin (in the cell membrane) and positive in the cell nucleus of neuroendocrine carcinoma cells (IHC 40 ×); F: Adenocarcinoma cells were strongly positive for CK20, while neuroendocrine carcinoma cells were positive (IHC 100 ×).