Women with breast cancer often don’t know what kind of tumors they have, a new study found.

Not knowing one’s tumor features isn’t necessarily tied to worse outcomes, but better knowledge might help women understand treatment decisions and take medications as directed, said Dr. Rachel Freedman, the study’s lead author from the Dana-Farber Cancer Institute in Boston.

Also, she said, cancer patients who understand the basis for their treatment are generally more satisfied with that treatment.

“Nobody to my knowledge has asked how much knowledge someone had of their own disease,” she added.

For the new study, published in the journal Cancer, Freedman and her colleagues asked 500 women from northern California about their breast cancers, which had been diagnosed between 2010 and 2011.

Participants were asked about their tumor grade, tumor stage and whether or not their cancer feeds off the hormone estrogen or a protein called human epidermal growth factor receptor 2 (HER2).

Fifty-five percent of women said they knew if their tumor fed off estrogen, and about a third said they knew their HER2 status. About a third said they knew their tumor’s grade, which is the cancer’s aggressiveness. And 82 percent of women said they knew their tumor’s stage, which is how advanced the cancer is.

Based on their medical records, only 56 percent of women reported the correct estrogen status, 58 percent reported the correct HER2 status and 57 percent reported the correct stage. Only about one in five women reported the correct grade.

Overall, only 8 percent of women correctly answered all four questions, but the lack of knowledge was more pronounced among minority women, the researchers report.

“Even though all these questions were low for all women, we did see difference by race and ethnicity,” Freedman said.

“What’s really nice about finding something like this is that it’s a modifiable problem,” Freedman said. “If you can improve education and provider awareness of this, you can do something about this in the clinic.”

Dr. Michelle Shayne of the James P. Wilmot Cancer Center at the University of Rochester School of Medicine and Dentistry in Rochester, New York, who was not involved in the study, told Reuters Health, “Breast cancer patients in general are a very savvy group of individuals."

They "tend to read a lot and bring a lot of clippings in to their oncologist and ask a lot of questions," she said, so the study findings surprised her.

The results show that oncologists need to tailor their discussions about cancer to individual patients as much as they tailor the treatments, she said.

Also, she said, cancer survivors should receive detailed treatment histories and information about their tumors for future medical care.

Freedman said that in her own practice, she’s been trying to explain patients' cancers in more detail, writing down the specifics and making sure they understand the information.

“I think this raises awareness of the issue,” she said. “This may be a more important issue than we previously appreciated.”