Regardless of whether HERV-K (HML-2) could induce infectivity in lymphoma and breast cancer or not, HERV-K could be considered as a biomarker in diagnosis of tumors (i.e., the discrepancy between the healthy controls and lymphoma cases was around 8 folds copies/mL) [91], specifically at the early stages of breast cancer that the load of HERV-K mRNA and antibodies directed against HERV-K Rec or Env or N9 are remarkably higher than healthy individuals [141], although antigenicity of HERV-K N9 is lower than HERV-K Rec and Env due to its small size [141]. This evidence concerns the gene ERVW-1 and lymphoma.