A particular case of large granular lymphocytes lymphoma

A patient with non-cutaneous lymphocytic lymphoma with leukaemic spread is reported. The large majority of the peripheral blood mononuclear cells formed rosettes with sheep erythrocytes (E), had receptors for the Fc portion of IgG (Fc gamma R) and displayed an unusual enzymatic profile. Part of these cells had also labile bound surface membrane IgG. The leukaemic cells were morphologically characterized as large granular lymphocytes (LGL) and consisted of two different types of cells: lymphoid cells and monocytoid cells. The histopathological diagnosis was T-cell lymphoma, pleomorphic type, diffuse. Despite their morphological heterogeneity, all the proliferative cells had the same immunological phenotype, showed normal ADCC activity but no NK activity. After three months, without specific treatment, the surface pattern changed: the cells resembled mature LGL and the NK activity increased. The cytochemical study of the leukaemic cells revealed an enzymatical peculiarity: besides an enzymatic profile characteristic for relatively mature LGL, the cells also displayed peroxidase activity. This unusual aspect--the expression by an individual malignant cell of markers believed to be restricted to a single cellular lineage--might be interpreted as a lineage infidelity or lineage promiscuity. The observation that this lymphoma developed in a patient with a long history of hypogammaglobulinaemia is of particular interest.