Follicular large cleaved cell (centrocytic) lymphoma: an unrecognized variant of follicular lymphoma

The World Health Organization classification of lymphoma recommends the subdivision of follicular lymphoma (FL) into 3 grades (FL1-3) based on the average number of centroblasts per high-power field in the neoplastic follicles, but does not recognize a form of FL characterized by a predominance of large cleaved cells (centrocytes) without enough centroblasts to meet the World Health Organization criteria for FL3. We have classified such cases as follicular large cleaved cell lymphoma (FLC) and, herein, describe the pathologic and clinical features of 72 cases of this entity. The features of FLC include a follicular growth pattern with pale follicles at low magnification and frequent follicular and/or interfollicular fibrosis. Cytologically, the cells are predominantly large cleaved cells with moderately coarse to fine chromatin, absent or inconspicuous nucleoli, and small to moderate amounts of pale cytoplasm. The mean nuclear diameter of the large cleaved cells was 10.1 μ, approximately twice that of small lymphocytes and similar to centroblasts. The t(14;18) was present in 83% of the cases, and a high proportion expressed BCL2 (84%), BCL6 (100%), and CD10 (88%) and had high Ki67 proliferation (81%). The clinical features of patients with FLC were similar to those with other types of FL, and survival was excellent with anthracycline-based chemotherapy plus rituximab. FLC is a variant of follicular lymphoma which should be recognized in future lymphoma classifications because the diagnosis of FLC may be important for the selection of therapy.