In addition to a high percentage of CDH1 mutations, some of which were associated with an aberrant E-cadherin expression pattern, these tumours seem to be characterized by higher frequency of mutations in genes related to aggressive behaviour, such as ERBB2, TP53 and KMT2C. The high frequency of treatable ERBB2 mutations in this and other previous series suggest that ERBB2 mutation testing should be considered in all ILC with nuclear grade 3. This evidence concerns the gene KMT2C and neoplasm.