Because this is the first study to be done in Tanzania on HER2 protein expression, there is no data available locally for comparison although, reports from elsewhere show that the expression of HER2 protein occurs in 13–20% of invasive ductal breast carcinoma and more than half (55%) of these cases were found to be hormonal receptor negative [47]. The gene discussed is ERBB2; the disease is invasive ductal breast carcinoma.