FCRL5 (Fc Receptor Like 5) , also known as CD307e, FCRH5, IRTA2, or BXMAS1, is a single-pass type I membrane protein belonging to the immunoglobulin receptor superfamily. It is encoded by a gene located on chromosome 1q23.1 and is primarily expressed in lymphoid tissues such as lymph node and spleen. FCRL5 functions as a dual regulator of B cell receptor (BCR) signaling and is implicated in B-cell development and lymphomagenesis. In multiple myeloma (MM), FCRL5 is considerably upregulated and has emerged as a promising immunotherapeutic target. Therapeutic strategies targeting FCRL5 include CAR-T cells, bispecific T-cell engagers (e.g., Cevostamab), and antibody-drug conjugates (ADCs).