Unexpected metastasis of intraductal papillary neoplasm of the bile duct without an invasive component to the brain and lungs: A case report

Figure 4 Microscopic findings of the bile duct tumor. A: The tumor showed the intraductal papillary proliferation of columnar cells with a high nuclear/cytoplasmic ratio; B: These neoplastic cells were entirely confined within the duct, and no invasion was identified (A: magnification × 20, B: magnification × 400); C-F: Immunohistological staining showed that the tumor cells were positive for CDX2, CK7, CK20, and Ki67.