CD27 and neoplasm: In our previous work, we had delineated that neoplastic arrest in HCLc most likely occurs at a stage of B-cell differentiation that straddles onset of SHM and deletional CSR [20,43], and as HCLc tumour cells do not express CD27 [1], suggests that SHM and CSR may occur at ectopic sites in origins of disease [44].