From the Division of Hematology, Mayo Clinic, Rochester, MN.

Supported in part by grants CA62242, CA85818, CA93842, and CA100080 from the National Cancer Institute, Bethesda, MD.

Individual reprints of this article are not available. Address correspondence to S. Vincent Rajkumar, MD, Division of Hematology, Mayo Clinic, 200 First St SW, Rochester, MN 55905 (rajkumar.vincent@mayo.edu).