In order to characterize whether a recently proposed monocytoid B-cell lymphoma (MBCL) is a distinct clinicopathologic entity, cases were collected from the two lymphoma files (K.N. and H.N.). The diagnosis of MBCL was based primarily on the described criteria, but several other limitations were also applied to increase the accuracy of case selection. By clinicopathologic features of 47 cases collected together with review of the literature, it is confirmed that a low-grade non-Hodgkin's lymphoma (NHL) which is difficult to be characterized based on the currently used classification systems does exist. However, the clinicopathologic features of MBCL were more heterogeneous than initially thought. Although MBCL and low-grade B-cell NHL arising from the mucosa-associated lymphoid tissue should be separated for the managements of patients with these NHLs, several lines of evidence indicate that these two NHLs are hematopathologically identical. It is stressed that NHLs should be classified based on the cells of origin, but not on the organs or systems involved.
