Follicular large cell lymphoma. An immunophenotype study

The authors investigated 17 cases of follicular large cell lymphoma using monoclonal antibodies applied to frozen sections. The neoplastic cells in 11 cases (65%) showed evidence of immunoglobulin expression similar to the reported percentage of immunoglobulin expressing diffuse large cell lymphomas and lower than seen in low grade follicular lymphomas. All cases showed expression of the B lineage markers TO15, B1, and 4G7, and HLA-DR. CALLA was present in all but 1 case, similar to that reported for follicular lymphomas, and much higher than reported for diffuse large cell lymphoma. Approximately one-half of the cases showed weak expression of Tac, 5 cases expressed B2 (C3d), and 3 cases expressed TO5 (C3b). Variable expression was seen for the Ki-67 antigen. A CR4/23+, B2+ TO5+ dendritic population was identified in all cases. An interfollicular host T-cell infiltrate was noted, mainly phenotypic helper cells. This study demonstrates that follicular large cell lymphoma has immunologic similarities to both diffuse large cell lymphoma and the low grade follicular lymphomas