Differential diagnosis with B-CLL is of paramount importance and the co-expression of CD20, CD5, and CD23 by neoplastic cells of B-CLL as well as the detection of a monoclonal rearrangement of the Ig genes in contrast to the polyclonality of T lymphocytes admixed with CD123+ PDC in TLE, allows for reaching the correct diagnosis [38]. This evidence concerns the gene FCER2 and B-cell chronic lymphocytic leukemia.