ERBB2 and triple-negative breast carcinoma: In 2020, Howard et al. studied feline mammary tumors, particularly feline mammary adenocarcinoma (FMA), as a model for triple-negative breast cancer (TNBC), a subtype of human breast cancer which does not express estrogen receptors or progesterone receptors, and does not overexpress human epidermal growth factor receptor 2 (HER2).