The medium cell sIg+, proplasmocytic lymphoma/leukemia. Positive and differential diagnosis with other B-lymphoblastoid neoplasias.

The authors describe the neoplasia of the only cell of the B-lymphocytic differentiation step, of which no lymphoma has yet been described: the cell intermediary between the memory B cell of the mantle zone, and the long-lived, marrow migrating and IgD or IgG secreting plasma cell, or mucosae migrating IgA secreting plasma-cell: they describe its neoplasia under the name of "medium cell cmu- sIg+ proplasmocytic lymphoma". It is defined by four characters: a) the homogeneous medium sized lymphoblastoid cells with one nucleolus per cell; b) the cmu- sIg+ marker as well as the CD38 and CD22; c) the t(11;14) translocation; and d) the poor prognosis and rapidly fatal evolution with a rapid conversion to the leukemic phase. The latter has probably been described, when the diagnosis is only made at this stage, as "B-prolymphocytic leukemia", which is nonsense, as the pre B-cells are cmu+ sIg-.