T-zone lymphoma with predominance of 'plasmacytoid T-cells' associated with myelomonocytic leukaemia--a distinct clinicopathological entity.

In this paper we present a further case of a new clinicopathological entity combining a rare type of non-Hodgkin lymphoma with a myelomonocytic leukaemia. The characteristic feature of the lymphoma is massive infiltration of the T-zones of lymph nodes by plasmacytoid cells originally described by Lennert in non-specific lymphadenitis. Two lymphoma cases of this type have recently been published, by Müller-Hermelink et al. who named the cells 'plasmacytoid T-cells' (PTC), and by Prasthofer et al. These three cases have similar clinical and pathological features and appear to form a distinct clinicopathological entity. In contrast to the two previously published cases the present lymphoma also contained irregular lymphoid cells accompanying the PTC in the lymph node lesion and focally infiltrating the bone marrow. An accumulation of polytypic IgG positive plasma cells was observed in the remaining lymph node follicles. Immunohistological analysis with a range of monoclonal antibodies showed the PTC of our case to be CD5(T1)+, CD4(T4)+, CD3(T3)-, CD8(T8)-, CD2(T11)-, and CD25(TAC)-, but HLA-DR+ and transferrin receptor positive. The nature of this peculiar lymphoid lesion and its relationship to myelomonocytic leukaemia are discussed.