Figure 1.

Immunohistochemical double staining for Cyclin D1 and CK 5/6 or CK 8/18 in papilloma (A B, original magnification × 200; a b, original magnification × 400) and in papillary carcinoma (C D, original magnification × 200; c d, original magnification × 400). The cytoplasm of the cells expressing CK 5/6 is stained pale red and CK 8/18 was stained red, whereas the cytoplasm of cells expressing CK 8/18 is stained red. The nuclei of Cyclin D1 positive cells are stained black. (A, a) Immunohistochemical double staining for Cyclin D1 and CK 5/6 in a papilloma. The Cyclin D1 positive cells were hardly detected in (A). (B, b) Immunohistochemical double staining for Cyclin D1 and CK 8/18 in a papilloma. There were a few Cyclin D1 positive cells detected in (B). Upon comparing (a) and (b), Cyclin D1 expression is clear in the cells that are positive for CK 8/18 in contrast to the cells that are positive for CK 5/6 in the papillomas. (C, c) Immunohistochemical double staining for Cyclin D1 and CK 5/6 in papillary carcinoma. The cells are not immunoreactive for CK 5/6. (D,d) Immunohistochemical double staining for Cyclin D1 and CK 8/18 in papillary carcinomas. Cyclin D1 (D) localizes in practically the same position compared with (C). The number of the Cyclin D1 positive cells (C, D) clearly increases, in contrast to (A) and (B). As in the papillomas, Cyclin D1 only appears in the cells that co-express CK 8/18.