Immunoglobulin gene rearrangements in immunomagnetically sorted CECs in MM patients with 13q14 deletion. PCR analysis demonstrated that in MM CECs, immunoglobulin genes were clonally rearranged. Sequence analysis showed that MM CECs carried the same immunoglobulin rearrangement as bone marrow plasma cells (Patient 1: VH3-11, D1-26, JH6; Patient 4: VH2-5, D3-3, JH4) BM PCs indicate bone marrow plasma cells.