ERBB2 and breast carcinoma: On the other hand, several investigations related to HER2 activation with a very low incidence (2%), in another way to breast cancer, which was absent of HER2 amplification by FISH and/or protein overexpression by IHC, showed HER2 gene mutations (such as V777L, L755S, D769H, V842I, G309A, etc.)(16, 17).