We identified 14 B-cell neoplasms with concurrent t(14;18) and chromosome 8q24 or c-MYC translocations shown by conventional cytogenetics or fluorescence in situ hybridization analysis. All cases assessed by conventional cytogenetics had a complex karyotype. There were 10 men and four women, with a median age of 55 years (range, 29-72). None of these patients had a history of follicular lymphoma. The biopsy specimens were obtained from bone marrow, lymph node, and extranodal sites. Morphologically, nine neoplasms had features of Burkitt or atypical Burkitt lymphoma/leukemia and three were diffuse large B-cell lymphoma with high-grade cytologic features. The remaining two cases were plasmablastic myeloma and low-grade B-cell lymphoma, respectively. All cases expressed BCL-2. The proliferation index assessed by using Ki-67 (MIB1) was 5% in the low-grade B-cell lymphoma, 80% in the plasmablastic myeloma, 90-95% in three cases of diffuse large B-cell lymphoma, and ranged from 90 to >99% in most Burkitt and atypical Burkitt neoplasms. The patient with low-grade B-cell lymphoma was treated with rituximab. All other patients received intensive combination chemotherapy. Two of these patients underwent bone marrow transplantation, and one patient received radiation therapy in addition to transplantation. The median follow-up period was 9 months (range, 3-81). In all, 10 patients died with a median survival of 9 months (range, 3-81). We conclude that most B-cell lymphomas with concurrent t(14;18) and 8q24/c-MYC translocations fall within the morphologic spectrum of diffuse large B-cell and Burkitt lymphoma. These neoplasms are high-grade and are associated with a poor prognosis. However, this combination of molecular abnormalities can also rarely occur in other neoplasms, such as the cases of low-grade B-cell lymphoma and plasmablastic myeloma in this study.