Cancer transmissibility across HLA barriers between immunocompetent individuals: Rare but not impossible

The axiom of human leukocyte incompatibility (HLA) incompatibility has always led scientists to consider cancer transmission between HLA-different individuals impossible. In fact, cancer transmission between individuals represents a frightening possibility in animal populations with limited HLA diversity or for rare cancers exploiting downregulation of HLA expression. We review here evidence from nonhuman models and settings for interhuman transmission.