Trisomy 12-associated, t(11;14)-negative mature B-cell leukemia with gene expression profile resembling mantle cell lymphoma.

Trisomy 12 can be seen in many different lymphoid neoplasms. However, many or most mature B-cell leukemias associated with isolated trisomy 12 are reported in the literature as chronic lymphocytic leukemia (CLL) or 'atypical CLL'. This study reports a case of a mature B-cell leukemia, morphologically and immunophenotypically similar to cases previously published as atypical CLL, in which cytogenetic evaluation revealed an isolated clonal trisomy 12 but no evidence of the mantle cell lymphoma-associated t(11;14)(q13;q32). Further analysis confirmed absence of cyclin-D1 expression. Subsequent lymph node biopsy revealed evidence of large cell transformation of the underlying chronic lymphoproliferative disorder. Gene expression profiling of the initial peripheral blood sample using a cDNA micro-array of approximately 10,000 expressed genes revealed a close resemblance between the reported case and 2 cases of known mantle cell lymphoma. When further compared to 7 known 'typical' CLL cases, the reported case was classified as mantle cell lymphoma by hierarchical cluster analysis. The case reported here raises interesting questions regarding the nature of cases reported previously as trisomy 12-associated CLL and reinforces the fact that other leukemic lymphoproliferative disorders should be included in the differential diagnosis of such cases. Further study is indicated to elucidate the nature and diversity of disorders previously reported as trisomy 12-associated chronic lymphocytic leukemia.