The mutated FH eliminates the hypoxia-inducible factor (HIF) prolyl-hydroxylase and enhances the hypoxia-inducible factor 1 alpha (HIF1alpha), which further affects downstream effectors, such as glucose transporter 1, erythropoietin, and vascular endothelial growth factor, and induces epigenetic changes, causing cell proliferation, metastasis, and tumor. This evidence concerns the gene HIF1A and neoplasm.