Characterization of C57BL/6 plasmacytomas lacking a c-myc translocation

BALB/c peritoneal plasmacytomas induced by a variety of agents are invariably associated with a c-myc translocation. In contrast, naturally arising bone marrow plasma cell tumors in C57BL/KaLwRij mice lack this translocation. This difference has led to the suggestion that these are 2 fundamentally different plasma cell diseases. Herein, we have analyzed 2 rare C57BL/6 peritoneal plasmacytomas in terms of characteristics associated with the bone marrow-derived lines. Like the bone marrow lines, these peritoneal plasmacytomas do not exhibit c-myc translocations, indicating that c-myc translocation is not an obligatory event in the development of all murine extramedullary plasmacytomas. However, myc is dysregulated at the mRNA level, indicating that myc overexpression may be fundamental to most plasma cell diseases but that dysregulation can occur by alternative mechanisms possibly reflecting different genetic backgrounds.