Diffuse intermediate lymphocytic lymphoma. A clinicopathologic study and comparison with small lymphocytic lymphoma and diffuse small cleaved cell lymphoma. Controversy has recently arisen as to whether diffuse intermediate lymphocytic lymphoma (ILL) should be considered a low-grade or an intermediate-grade non-Hodgkin's lymphoma for clinical purposes. Therefore, the authors performed a clinicopathologic study to determine the biologic course of diffuse ILL (40 cases) and compared it with small lymphocytic lymphoma (SLL; 51 cases) and diffuse small cleaved cell lymphoma (DSCCL; 14 cases). They found that patients with diffuse ILL having pseudofollicular proliferation centers (PC) had a significantly longer median survival (84 months) than those without PC (46.5 months; P = 0.03). The median survival of patients with SLL was 72 months, whereas those with DSCCL had a median survival of only 18 months. Based on these findings, the authors conclude that diffuse ILL with PC should be included in the low-grade category of SLL for clinical purposes, whereas diffuse ILL without PC (true diffuse ILL) should be considered an intermediate-grade non-Hodgkin's lymphoma. True diffuse ILL is similar to centrocytic lymphoma in the Kiel classification and should be accorded a similar status in a modified Working Formulation. 