In February, the World Health Organisation declared that breast cancer had overtaken lung cancer as the world's most commonly diagnosed cancer.
Breast cancer is the most common cancer in women in Singapore and one in 13 women will develop it over her lifetime.
Fifty years ago, in comparison, the figure was one in 45 women, according to the Breast Cancer Foundation, citing data from the Singapore Cancer Registry.
As cases have risen over the years, so has the number of younger women being diagnosed with the condition, says Dr Tira Tan, a consultant from the department of breast and gynaecology in the division of medical oncology at the National Cancer Centre Singapore (NCCS).
About 10 per cent of women with newly diagnosed breast cancers are below the age of 40, she adds.
The NCCS saw more than 720 such women from 2015 to last year - around 5 per cent more than in the preceding five-year period.
"Younger women are more likely to be diagnosed with more aggressive forms of breast cancers such as triple-negative breast cancer, Her2 positive breast cancer or high-grade oestrogen receptor positive breast cancer," adds Dr Tan, who is also head of the Young Women's Programme at NCCS.
Triple-negative breast cancer accounts for about 15 per cent of all breast cancers, says Dr Ong Kong Wee, a senior consultant breast surgeon from the newly opened Mount Elizabeth Breast Care Centre at Mount Elizabeth Novena Hospital.
"It is called triple negative because the tumour cells lack estrogen, progesterone and Her2 receptors on the cell surface. The absence of these receptors limits the treatment options of this cancer, which together with its more aggressive nature, make the prognosis or outcome for patients worse."
Noting that about 4 per cent of breast cancers in women below the age of 45 are diagnosed during pregnancy or in the postnatal period, Dr Tan says: "It has been reported that the incidence of pregnancy-associated breast cancers is increasing in part due to childbearing at an older age and increased awareness and detection."