Cyclin D-1 protein over-expression is not associated with gene amplification in benign and atypical apocrine lesions of the breast.

Cyclin D-1 protein over-expression and/or gene amplification have been shown to be frequent events in subsets of breast carcinomas. Cyclin D-1 is generally considered as a weak oncogene, and its over-expression has been shown to occur in occasional benign breast lesions. In a previous series, we have shown that cyclin D-1 was over-expressed in subsets of apocrine metaplasia (APM) and apocrine adenosis (AA) of the breast and that such over-expression was mostly associated with a significant increase in the proliferative capacity of these lesions. We examined the mechanisms involved in cyclin D-1 over-expression in apocrine lesions. A total of 41 cases were analysed in this study. The cases were divided into: 18 cases of APM and 23 cases of AA. All cases analysed had been previously analysed by immunohistochemistry, and all showed over-expression of the cyclin D-1 protein. Fluorescence in situ hybridisation (FISH) was performed using a dual cyclin D-1 (spectrum orange)/chromosome 11 centromere (spectrum green) DNA probe. The results showed that none of the cases studied had concomitant gene amplification. These results suggest that other post-transcriptional mechanisms might be responsible for cyclin D-1 protein over-expression in benign apocrine lesions. Further studies are needed to understand the mechanisms involved in abnormal cyclin D-1 expression in these lesions.