Contrarily to previously published results [12], describing an antitumor effect of resveratrol in a HER2+/ERα- breast cancer experimental model, here we have found that resveratrol, given at the same reported dose, regimen and administration way, did not prevent nor delay tumor onset; instead, significantly accelerated cancer development in Δ16HER2 females that spontaneously develop HER2+/ERα+ mammary carcinomas. The gene discussed is ERBB2; the disease is breast carcinoma.