Latinas and older, poorer women all are more likely to have lymph nodes under the armpit removed unnecessarily during breast cancer surgery, according to a new study, Reuters reports.

That’s despite 2005 guidelines recommending a gentler surgery that spares most of the lymph nodes, avoiding side effects like pain, swelling and numbness down the line.

Based on a California cancer registry, researchers found that more than a third of about 18,000 women who had undergone mastectomy for early-stage breast cancer had had their lymph nodes removed as well.

Yet all of these women had node-negative tumors, meaning the cancer had not spread beyond the breast.