Thus, together with the recently reported pre-pro/pro- B- cell differentiation of MCC, i.e. TdT and PAX-5, immunoglobulin (Ig) expression and Ig rearrangements [18, 19], the functional PI3K p110δ expression in MCC might add another tesserae in the discussion of the cellular origin of MCC. This evidence concerns the gene DNTT and Merkel cell skin cancer.