BCL-1 (PRAD-1/cyclin D-1) overexpression distinguishes the blastoid variant of mantle cell lymphoma from B-lineage lymphoblastic lymphoma

Abstract

The blastoid variant of mantle cell lymphoma (MCL-BV) can occur de novo or can represent a morphologic transformation of MCL associated with aggressive clinical disease. Its cytologic appearance is very similar to that of lymphoblastic lymphoma (LBL) because of its characteristic nuclear features and high proliferative rate. To assess the usefulness of antibodies to cyclin D-1 (BCL-1/ PRAD-1), CD99 (12E7), CD34, and TdT in distinguishing between MCL-BV and LBL in formalin-fixed, paraffin-embedded tissue, we studied from the Stanford data base 10 cases originally diagnosed as B-lineage LBL, 5 MCL-BVs, 2 cases thought likely to represent MCL-BV, and 2 blastic lymphomas whose morphology and immunophenotype were indeterminate. Six (60%) of 10 LBLs stained with CD99, as opposed to none of 7 MCL-BVs. Four (40%) of 10 LBLs reacted with CD34, as compared with none of 7 MCL-BVs. Eight (89%) of nine LBLs were positive for TdT, but all of the four MCL-BVs tested were negative. In contrast, the anti-cyclin D-1 antibody stained the nuclei of all of the MCL-BVs and none of the LBLs tested. On the basis of our evaluation, the probable MCL-BV cases were considered to be definite MCL-BV. Of the indeterminate cases, one was considered to be LBL, whereas we felt that the other represented MCL-BV. We conclude that staining formalin-fixed, paraffin-embedded, high-grade lymphomas with anti-cyclin D-1 antibody is useful in confirming the diagnosis of MCL-BV, whereas positive reactions with CD99, CD34, and particularly TdT are more characteristic of LBL.