Background: To evaluate the expression levels of cyclin D1 in breast papillomas and papillary carcinomas, and to analyze the types of cells that co-express cyclin D1 with cytokeratin 5/6 (CK 5/6) or with cytokeratin 8/18(CK 8/18).
Methods: Fifty-nine cases of papillary lesions including 36 papillomas and 23 intracystic papillary carcinomas were examined. Cyclin D1, CK 5/6 and CK 8/18 expression levels were evaluated by double immunostaining.
Results: Cyclin D1 is highly expressed in papillary carcinomas (27.54% ± 15.43%) compared with papillomas (8.81% ± 8.41%, p < 0.01). Cyclin D1 is predominantly expressed in cytokeratin 8/18- expressing cells, rather than in cytokeratin 5/6-expressing cells, regardless of the type of lesion. In papillomas, cyclin D1 exhibited a mean 11.42% (11.42% ± 10.17%) co-expression rate with cytokeratin 8/18 compared with a mean 2.50% (2.50% ± 3.24%) co-expression rate with cytokeratin 5/6 (p < 0.01). In papillary carcinomas, cyclin D1 exhibited a mean 34.74% (34.74% ± 16.32%) co-expression rate with cytokeratin 8/18 compared with a co-expression rate of 0.70% (0.70% ± 0.93%) with cytokeratin 5/6 (p < 0.01).
Conclusions: The increase in cyclin D1 suggests an association of cyclin D1 staining with papillary carcinomas. Although cyclin D1 is an effective marker for the differential diagnosis of other papillary lesions, it cannot be used to distinguish between papilloma and papillary carcinoma lesions because its expression occurs in both lesions. Our results show that cyclin D1 and CK 5/6 staining could be used in concert to distinguish between the diagnosis of papilloma (cyclin D1 < 4.20%, CK 5/6 positive) or papillary carcinoma (cyclin D1 > 37.00%, CK 5/6 negative). In addition, our data suggest that cyclin D1 is expressed only in the cancer stem or progenitor cells that co-immunostained with CK 8/18 in papillary carcinomas, and predominantly with CK 8/18 in the papillomas.
Virtual slides: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/7299340558756848.