L3MBTL4 and neoplasm: We found that the inherent propensity of Epi‐LumB tumors to acquire CpG island promoter methylation events affected a subset of previously established tumor suppressor genes (based on the catalogue of 716 TSG, see Zhao et al., 2013) of which at least five are shown to be strongly down‐regulated upon CpG promoter methylation, i.e. L3MBTL4, ID4, IRX1, PTCH2 and RASSF10 (Table 1).