CD274 and mastocytosis: The PD-L1 expression in neoplastic mast cells that has been confirmed by these studies warrants further investigation of the tumor-immune interactions in mastocytosis to clarify possible breakpoints in the PD-L1 expression by type of mastocytosis, as well as to clarify the role of the immune checkpoint molecule expression in tumor infiltrating lymphocytes, and to explore a possible role for immune checkpoint inhibition.