ADAM12 and neoplasm: To summarise, here we report for the first time that: (i) ADAM12 is hypomethylated and overexpressed in TNBC cases relative to non-neoplastic breast tissues, (ii) this epigenetic alteration is already present in the adjacent-to-tumour tissue and in cfDNA, (iii) ADAM12 promotes TNBC cell proliferation, migration and doxorubicin-resistance, and (iv) low levels of ADAM12 methylation are associated with shorter OS in TNBC patients.