abnormal pre-B cell morphology MP:0002403 MPheno.ontology These cells express the mu heavy chain in both the cytoplasm and on the cell surface; in addition to the mu heavy chain, other cell surface markers include CD45R, MHC class II, CD19, CD20, CD38, and CD40. abnormal pre-B-cell morphology any structural anomaly of the cells in the B lymphocyte lineage that have undergone VDJ rearrangement of the immunoglobulin heavy chain and are in the process of V-J rearrangement of the light chain: these cells express mu heavy chain on the cell surface abnormal B cell morphology