A new study has reported a progressively increasing frequency of estrogen receptor negative (ER-) and triple-negative disease among breast cancer patients according to their degree of African ancestry. Triple negative breast cancer is a subtype of breast cancer that is ER-, progesterone receptor negative (PR-), and human epidermal growth factor receptor 2 (HER2) negative. Investigating the characteristics of breast cancer in women with African ancestry may serve to identify markers for breast cancer risk assessment and treatment of triple negative disease. The study included 581 African-American and 1,008 Caucasian U.S. women diagnosed at the Henry Ford Health System, as well as 75 Ghanaian patients diagnosed or treated at the Komfo Anokye Teaching Hospital in Kumasi, Ghana. Average age at diagnosis was 48.0 years for the Ghanaian, 60.8 years for the African-American, and 62.4 for the Caucasian-American women.

The Ghanaian women had the highest proportion of ER- tumors (76%), followed by the African Americans (36%) and Caucasians (22%). The fraction with triple negative disease was also remarkably high among the Ghanaian women (82%) compared to the African-American (26%) and white (16%) women. All of the Ghanaian women's tumors could be felt by hand and were locally advanced upon diagnosis — the majority (76%) were grade 3. A total of 147 of the U.S. women were diagnosed at stage III or IV; of these, 67.5% of the African Americans and 44.6% of the Caucasians were grade 3. Among only the palpable, grade 3 tumors, Ghanaians had the highest rate of triple-negative disease (82.2%), followed by African Americans (32.8%) and Caucasians (10.2%). The authors conclude that the study demonstrates progressively increasing frequency of ER- and triple-negative breast cancer among breast cancer patients according to their degree of African ancestry.