PTEN and neoplasm: MiR-21 is one of the most extensively studied cancer-related miRs and might play an ever-expanding role in most cancers.[38] miR-21 may serve as a key regulator of oncogenic processes, including tumor growth, migration, and invasion.[39] Elevated miR-21 expression levels have been found to be associated with poor outcomes in cancer patients.[40] miR-21 may target the pro-apoptotic phosphatase and tensin homolog (PTEN) and promote tumor cell proliferation, which, in turn, may inhibit the apoptosis of tumor cells in TNBC cell lines in vitro.[22]