The major lymphoid inhabitant of the follicular mantle is the mantle cell, an immunologically naïve B cell. It is the putative cell of origin of mantle cell lymphoma (MCL), the cells of which have similar morphologic, immunophenotypic, and molecular characteristics to the normal B lymphocytes of the mantle zone. In the past year a number of advances have been made in the biology of the normal mantle cell, its interactions with the other constituents of the follicular and mantle zone microenvironments, and the development of neoplasia in this cell population. In addition, new developments in diagnostic molecular pathology have been used to more readily identify cases of MCL. The authors summarize these new advances in the understanding of the biology of the mantle cell and newer ancillary techniques in the diagnosis of lymphomas arising from this cell type.