However, multiple subsequent studies have found that FEN1 was overexpressed in a variety of solid tumors, and therefore, it was regarded as a marker of poor prognosis.24–28 This evidence suggests two mechanisms by which FEN1 promotes the initiation and progression of tumors: genomic instability caused by FEN1 mutation that leads to tumorigenesis and overexpression of FEN1 that promotes the proliferation of tumor cells. Here, FEN1 is linked to neoplasm.