The Breast Cancer Foundation is urging all women to undergo some form of breast checks, regardless of age.
In the wake of Cabinet minister Nikki Kaye's diagnosis, Breast Cancer Foundation spokeswoman Adele Gautier says early detection is key.
"Breast cancer is most common in women over 50, but before that it's really important to keep an eye on your breasts, and from the age of 40 start getting mammograms."
Ms Kaye, 36, is the minister for ACC, Civil Defence and Youth Affairs. She revealed her diagnosis on Monday, going on immediate leave from her portfolios.
Ms Gautier says woman aged under 40 should always check for lumps.
"What matters is that they need to understand the normal look and feel of their breasts, knowing what that is so they can report any changes to their doctor."