A recent study from the University of Iowa shows that cases of primary breast lymphoma (PBL) have increased over the last four decades and continue to increase among younger women and for some subgroups.

According to the researchers, this is the largest contemporary study describing presentation, incidence, initial local therapy, and outcomes for women with PBL. The study, published in the Journal of the National Cancer Institute, looked at data spanning four decades.

Researchers found that the incidence of PBL increased from 0.66/1,000,000 women in 1975-1977 to 2.96 in 2011-2013. Overall, incidence of PBL has remained relatively stable in recent years, but continues to increase for women under 50 years of age.

Although reasons for this increase remain unclear, the study concedes that the advent of wide-spread breast imaging might have enhanced diagnostic sensitivity for PBL, even though most cases are not diagnosed in this way.

Researchers also note that the use of cosmetic implants increased 294.8% from 1997-2007, fell 21.9% from 2007-2009 (concurrent with the Great Recession), and has remained fairly stable from 2009-2015, generally reflecting the overall trends in PBL cases.

However, Mary Schroeder, assistant professor in the division of Health Services Research at the University of Iowa and the study’s senior author, cautions against correlating implant use with overall PBL trends.

“In 2011, the FDA identified a possible association between breast implants and the development of a particular type of PBL: anaplastic large cell lymphoma (ALCL),” Schroeder says. “Even so, ALCL comprises only a very small percentage of PBL, and thus do not explain the observed increases in PBL incidence overall.”

The study suggests that future work in this area should focus on confirming trends in the data and creating a better understanding of the underlying causes of PBL.

Co-authors include Paul Romitti, professor of epidemiology, and Brian Link, professor of internal medicine, both at the University of Iowa; Alexandra Thomas, formerly with the UI and currently professor of hematology and oncology at Wake Forest University; and Sean Altekruse, formerly with National Cancer Institute and currently with the National Heart, Blood, and Lung Institute.

This work was supported in part by the University of Iowa Holden Comprehensive Cancer Center Population Research Core, which is supported in part by the National Institutes of Health/National Cancer Institute grant P30 CA086862.