Stage I and stage II infiltrating ductal carcinoma of the breast analyzed for chromosome 8 copy number using fluorescent in situ hybridization.

We previously reported the results of 30 informative samples (from a total of 34 specimens gathered) of archival breast cancer tissue, including infiltrating ductal carcinoma (NOS), ductal carcinoma in situ, lobular carcinoma, papillary carcinoma and benign lesions of the breast. The study was conducted using fluorescent in situ hybridization (FISH) and a chromosome 8 alpha-satellite probe. Subsequently, a total of 34 cases of infiltrating ductal carcinoma of the breast (NOS, 17 cases stage I and 17 cases stage II) were studied, again using interphase cytogenetics. The aim of the present study is to confirm and extend the results of our initial study of stage I and stage II disease. Towards this end, 36 additional specimens of formalin-fixed paraffin-embedded breast cancer tissue have been analyzed cytogenetically under blinded conditions for the frequency of abnormal chromosome 8 copy numbers using FISH and the previously described protocol optimized for our laboratory. Of these, 18 were stage I and 18 were stage II. The frequency of trisomy 8 among stage I tumors was found to be 28% (5 out of 18). The frequency of trisomy 8 among stage II tumors was found to be 61% (11 out of 18). These results, while less striking, are consistent with those reported in our initial study of stage I and stage II disease, where the frequencies of trisomy 8 among stage I and stage II tumors were 24% (4 out of 17) and 82% (14 out of 17). These results not only establish that chromosome 8 trisomy is a recurrent finding in breast cancer, but also confirm that a higher frequency of trisomy 8 was observed with a higher clinical stage (stage II) than with a lower stage (stage I). It will be of interest to extend the findings in stage I and stage II breast cancer to other stages as well.