Contrary to existing understanding, long-term follow-up of patients with two types of breast tissue abnormalities suggests that both types of abnormalities have the same potential to progress to breast cancer.
The study, published in Cancer Prevention Research, a journal of the American Association for Cancer Research, challenges current understanding that atypical ductal hyperplasia leads to breast cancer in the same breast, while atypical lobular hyperplasia may not be a direct precursor of breast cancer, but may indicate equal risk of breast cancer across both breasts.
“Ours is the first report with sufficient numbers of both types of atypia and long-term follow-up for breast cancers that compared the side of breast that had atypia with the side of breast in which cancer arose and the timeframe when the cancers developed,” said Lynn Hartmann, professor of oncology at the Mayo Clinic. “We showed that even though the two types of atypia look different histologically, they behave quite similarly in terms of what happens to patients.”
Hartmann and colleagues identified 698 women from the Mayo Benign Breast Disease Cohort who had biopsy-confirmed atypia; 330 of them had ADH, 327 had ALH, and 32 had both. The investigators followed these women for an average of 12.5 years, and 143 of them developed breast cancer.
The investigators found that the ratio of breast cancer in the same breast in which the atypia was detected versus in the opposite breast was the same, 2:1, for both ADH and ALH.
A similar number of women with either ADH or ALH developed breast cancer in the same breast within five years of diagnosis, which led the authors to suggest that, like ADH, ALH may also be a precursor in addition to being a risk indicator.
The study also found that ALH predominantly resulted in ductal cancer of the breast, which is a similar outcome as with ADH. Both ADH and ALH resulted in invasive ductal cancers, of which 69 percent were of intermediate- or high-grade. About 25 percent of them had spread to the lymph nodes. The pattern of cancers in these patients resembled those seen in the general population.
