In total, BCL9L mutations and/or deletions occurred in 14% of MSS CRC (26/186, 5 mutations and 21 deletions), the majority of which (23/26) retained a wild-type (WT) copy of BCL9L while biallelic alterations of BCL9L occurred in only three samples. The gene discussed is BCL9L; the disease is colorectal carcinoma.