The DNA profile of breast cancer in situ.

The nuclear DNA content of 46 mammary adenocarcinomas in situ was measured by means of image cytometry in 4-microns-thick Feulgen-stained histological sections. Aneuploidy was found in 23 cases (50%), whereas the other 23 cases exhibited a diploid DNA distribution pattern. Intraductal carcinoma, the most common subtype in the present study, was found to be aneuploid in 19 cases (63%), with the comedo variant showing aneuploidy in as many as 10 of 11 cases (91%). In contrast, lobular and papillary carcinoma in situ exhibited only 17% and 0% aneuploidy, respectively. The percentages of aneuploid and diploid DNA profiles of the in situ lesions in the present study are almost identical to those observed in invasive breast adenocarcinoma. This indicates that the DNA distribution pattern characteristic for an individual breast adenocarcinoma is already established at the in situ stage, i.e., it occurs before invasiveness and does not progress from a euploid to an aneuploid pattern. In clinical routines DNA ploidy measurements may be of help to distinguish between e.g., hyperplasias and in situ lesions and may also indicate in which direction the malignancy potential of in situ lesions will develop.