It was found by our current study that about 45.6% of studied female breast cancers were triple negative (ER−/PR−/HER2-) or TNBC which is comparable but higher than in a previous Tanzanian report (38.4%); and well in concordance with the incidence of47% in African American women in contrast to the 22% in white women [23, 51]. The gene discussed is ESR1; the disease is breast cancer.