FGF21 and cancer: As an unfolded area, the increasing roles of FGF21 generate a series of inspiring ideas, such as whether exclusive FGF21 secretion ability confers liver extra-hepatic functions, whether endocrine FGF21 is the holistic hub point for interorgan crosstalk, whether there are concomitant modulators that collaborate with FGF21 or whether FGF21 is an actionable biomarker with therapeutic values for cancers.