Using a dicotomised HER2 grouping into immunonegative (0 - 1+ classes) and immunopositive (2+ - 3+ classes) groups, we also found a significant positive association between HER2 and MMP-1 expression in tumour cells (p = 0.0086) and in stromal cells (p = 0.0038). Here, MMP1 is linked to neoplasm.