The differential diagnosis of B‐CLL was established according to the WHO classification as follows: the clonality of the neoplastic lymphocytes was confirmed by both surface and intracellular kappa/lambda immunoglobulin light chain expression, and all cells had the following characteristic surface phenotype: CD19+/CD5+/CD23+/CD20‐low+/CD22‐low+/CD43+/CD103−/CD11c− (Fig. S1). Here, FCER2 is linked to B-cell chronic lymphocytic leukemia.