A major new study published in the Journal of the National Cancer Institute shows just how vexing uncovering vast differences around the country in how ductal carcinoma in situ (DCIS) growths are removed — suggesting some women are overtreated and others undertreated — and giving new urgency to efforts to educate patients about their choices.

Studies have shown that 85% to 90% of high-grade DCIS lesions and 50 percent of all DCIS lesions have HER-2/neu protein on their cell surface. However only 25% to 30% of invasive breast cancers are HER-2 positive. The reason underlying the percentage variation between HER-2 positive DCIS lesions and HER-2 positive invasive breast cancer tumors is unknown.