Perhaps your mother told you. Or your doctor. Maybe you learned it in gym class.
For me it was all three: "Once a month, do a breast self-exam," they all said. "Use your fingertips in a circular motion to feel for lumps." (My mom, a nurse, even brought home a fake breast that I could practice on.)
So I was stunned when a physician in Glasgow, Scotland, criticized a campaign aimed at getting women to do their own breast checkups.
"Teaching women to examine their breasts regularly has been shown not to reduce deaths and actually increases the chances of a benign biopsy result," general practitioner Margaret McCartney of Glasgow wrote Tuesday in a letter to BMJ.
McCartney was prompted to pen the commentary because of a promotion in the The Sun tabloid, called "Check 'em Tuesday." It calls for women to ... um ... "cop a feel of their boobs" and then post pictures on Facebook and Twitter all in the name of cancer prevention.
The risque campaign replaces the photos of topless women that are a staple of the tabloid's Page 3.
McCartney worries the campaign will do more harm than good. It will make women think they're reducing their risk of dying from cancer, when there's no evidence to back up that claim.
She cites a large study in 2002 with more than 250,000 Chinese women. The scientists didn't find any difference in mortality rates from breast cancer between the women who were taught self-examination and those who weren't. But the former did find more benign lumps.
The U.S. Preventive Task Forces Services agrees with McCartney and recommends against teaching breast self-examination.
But oncologist Victoria Seewaldt at the Duke Cancer Center says it's too early to throw out self-exams altogether. They're too important for finding fast-growing cancers, she says, that other types of screening miss.
It's the way we're doing these checkups that needs revamping, she says.
"I run a highfalutin, fancy research-based, early detection facility with very expensive MRIs," Seewaldt says. "But we often turn to simple self-exams because with these very aggressive forms of cancer women can find lumps."
But forget about using your fingertips, Seewaldt says. "When you go over the breast with your fingertips, you feel all the structures inside the breast," she says. "You get too much information. Women often get freaked out. ... When I did my first breast exam, I felt like I found 40 cancers."
Instead, Seewaldt and her team tell women to "give your breast a high-five." Use the back of your hand to feel for lumps. Or get a gentleman or potential partner to help. "They're good at finding lumps, too," she says.
And don't overthink it. "When women find a breast lump, they say, 'I was putting my bra on and something caught.' Or, 'I reached to wash myself and there was lump,' " Sweewaldt says. "Going in with the idea that we're doing a cancer-finding expedition is really not a good idea."
Seewaldt is quick to point out that she doesn't know if the high-five or getting a partner to help works better than the traditional fingertip circles for finding the lumps. But she's ready to see clinicians go figure out what's best.
"The door for testing [the efficacy of self-examination] shut after the 2002 study in China," she says. "That was the final word. No one was going to do more studies. That was it."
But that study, Seewaldt thinks, isn't applicable to women in the U.S. today. "Breast cancer was a rare illness in China then, and the women were very young," Seewaldt says. "So it was like studying breast cancer in men in the U.S."
And the therapies available to the women in the study were limited compared with what American women have today. "You can find all the breast cancer you want. But if you do a lousy job of treating it, you're going to die of it."
So the jury is still out on self-exams. But there's something both doctors agree on: See your doctor, if you find a lump.
"And be persistent," Seewaldt says. Yearly exams aren't a bad idea either, she adds. "If you are at high risk, we recommend two exams a year."