Cellular proliferative activity of mammographic normal dense and fatty tissue determined by DNA S phase percentage.

A prospective study was undertaken to evaluate associations among mammographic normal dense and fatty tissue, benign histologic findings, and cellular proliferative activity determined by DNA S phase percentages. Mammographic and histologic findings of benign, normal dense and fatty tissue contained in 100 excised specimens were cross-tabulated with flow cytometric DNA S phase percentages of needle aspirates obtained under radiographic guidance. Histologic evidence of atypia or hyperplasia was present in 21 (32%) of 66 fatty tissue samples and 11 (32%) of 34 dense tissue samples (p = NS). The median S phase percentages were identical for mammographic fatty and dense tissue (median % S phase = 5.35). The frequency of high S phase percentages (above the median) was not significantly different for tissue containing atypia or hyperplasia, 47% (15 of 32), as compared to tissue containing other benign histology, 52% (35 of 68) (p = NS). These frequencies were similar in women 49 and younger or 50 and older. These data show that mammographic normal dense and fatty tissues contain similar frequencies of histologic atypia or hyperplasia and low and high cellular proliferative activity determined by DNA S phase percentages in women aged 49 and younger and 50 and older.