Mantle cell lymphoma (MCL) is one of the rarer of the non-Hogkin's lymphomas, comprising about 6% of NHL cases. There are only about 15,000 patients presently in the U.S. (The prevalence seems to be somewhat higher in Europe.) While it is difficult to treat and seldom considered cured, investigations into better treatments are actively pursued world-wide. Median survival times were about 3 years, but are now estimated as approaching 6 years for new patients.