FCRL4 and neoplasm: Existing studies suggest that circulating tumor DNA (ctDNA) (7), PD-L1 expression (9), tumor mutational burden (TMB) (10), and the transcriptomic characteristics of Fc Receptor-Like 4 Positive (FcRL4+) Fc Receptor-Like 5 Positive (FcRL5+) memory B cells and CD16+ CX3CR1+ monocytes (11) may serve as predictors of response to immunotherapy.