MIR15A and B-cell chronic lymphocytic leukemia: However, 16 out of 46 CLL cases (35%) in the same cohort with a negative result for del(13q) using the commercial FISH probe were positive for the deletion of MIRN16-1/MIRN15A using the custom probe (also called “unidentified” del(13q)/MIRN16-1/MIRN15A).