The complex profile of each subtype is determined using molecular and genetic information from tumor cells.
Most studies divide breast cancer into four major molecular subtypes: Luminal A Luminal B Triple negative/basal-like HER2 type.
These subtypes also appear in ductal carcinoma in situ (DCIS).
Other less common molecular subtypes, including claudin-low and molecular apocrine types.
At this time, molecular subtypes are used mostly in research settings.
Prognosis and treatment decisions are guided mainly by tumor stage, tumor grade, hormone receptor status and HER2 status.
Luminal tumor cells look the most like cells of breast cancers that start in the inner cells-the luminal cells lining the mammary ducts.
Luminal A tumors tend to be: Estrogen receptor-positive (ER-positive) HER2 receptor-negative (HER2-negative) and tumor grade 1 or 2.
About 30-70 percent of breast cancers are luminal A tumors.
Of the four subtypes, luminal A tumors tend to have the best prognosis, with fairly high survival rates and fairly low recurrence rates.
Among women with luminal A disease age 40 and younger ARE more than twice as likely die of disease, compared to women age 51-60.
Luminal tumor cells that look like those of breast cancers that start in the inner luminal cells lining the mammary ducts.
Luminal B tumors tend to be ER-positive. They may be HER2-negative or HER2-positive.
Women with luminal B tumors are often diagnosed at a younger age than those with luminal A tumors.
Compared to luminal A tumors, they also tend to have a poorer prognosis including: Poorer tumor grade, Larger tumor size, Lymph node-positive.
About 10-20 percent of breast cancers are luminal B tumors.
Patientswith luminal B tumors tend to have fairly high survival rates, although not as high as those with luminal A tumors.
Among women with luminal B disease younger women have a greater cancer mortality.
Triple negative breast cancers are: Estrogen receptor-negative (ER-negative) Progesterone receptor-negative (PR-negative) HER2-negative
There are several subsets of triple negative breast cancer.
One subset is basal-like.
Basal-like tumors have cells that look similar to those of the outer basal cells surrounding the mammary ducts.
Most triple negative tumors are basal-like and most basal-like tumors are triple negative.
Not all triple negative tumors are basal-like and not all basal-like tumors are triple negative.
About 15-20 percent of breast cancers are triple negative/basal-like.
Basal-like tumors tend to occur more often in younger women and African-American women, and more common among Hispanic women compared to white women.
Most BRCA1-related breast cancers are both triple negative and basal-like.
Triple negative/basal-like tumors are often aggressive and have a poorer prognosis compared to the ER-positive subtypes luminal A and luminal B tumors.
Most HER2 type tumors are HER2-positive, about 30 percent are HER2-negative.
HER2 type tumors tend to be ER-negative PR-negative, lymph node-positive, poorer tumor grade.
About 5-15 percent of breast cancers are HER2 type
Women with HER2 type tumors may be diagnosed at a younger age than those with luminal A and luminal B tumors.
Triple negative/basal-like tumors appear to be more common among black women (especially before menopause) compared to white women.
Triple negative/basal-like tumors may also be more common among Hispanic women compared to white women.
Prevalence rates of luminal B and HER2 type tumors do not appear to differ by race.
Higher rates of triple negative/basal-like tumors may explain, to some degree, the poor prognosis of breast cancers diagnosed in younger black women.
Also, luminal A tumors, which have the best prognosis of the subtypes, occur less often in premenopausal African-American women compared to postmenopausal African-American women and compared to white women of either menopausal status.
Among women with HER-2 positive or triple negative breast cancer there is no greater mortality risk among women 40 and under compared to women age 51-60.
Age matters in women with hormone sensitive sub-tumors, but does not appear to matter, or at least not as much in women with triple negative breast cancer or HER-2 positive breast cancer.
The five-year survival rate for triple negative breast cancer is 77%.