1. From the Department of Haematology, Royal Postgraduate Medical School and Hammersmith Hospital, London (P.H., S.M.L., M.B., L.L., J.V.D.); the Haematological Malignancy Diagnostic Service, Institute of Pathology, General Infirmary at Leeds, Leeds, United Kingdom (P.H.); and the Department of Human Genetics, Memorial Sloan-Kettering Cancer Center, New York (M.B., L.L.).