Mantle-zone lymphoma. An immunohistologic study.

Mantle-zone lymphoma (MZL) is a histologically distinctive variant of follicular lymphocytic lymphoma which is characterized by a proliferation of atypical small lymphoid cells as wide mantles around benign-appearing germinal centers. Immunoperoxidase stains were performed on fixed and processed lymph nodes from four patients with MZL. Three cases were of the intermediate lymphocytic type, and one was of the small cleaved lymphocytic type. In all cases, the small lymphoid cells of the mantle zones did not stain. A monoclonal population (IgM, lambda) of plasma cells and large lymphoid cells was demonstrated predominantly in the paracortical areas in one case. In all cases, small numbers of plasma cells and large lymphoid cells in the follicle centers stained in a polyclonal pattern, confirming the benign nature of the centers. These findings suggest that follicular lymphomas of the mantle-zone type are exceptions to the theory that follicular B-cell lymphomas are derived from follicular center cells. Apparently, the lymphoid cells of MZL home to the mantle zones of secondary follicles, where they surround, proliferate, and eventually obliterate residual benign germinal centers.