Monocytoid B-cell reaction associated with peripheral T-cell lymphomas.

Benign monocytoid B-cells (MBCs) proliferation was reported to occur in various lymphoproliferative disorders, but not in peripheral T-cell lymphomas (PTCL). In our review of fifty three nodal-based, low and high grade PTCL, MBCs were identified histologically and immunohistochemically in eight of the cases. They included: chronic lymphocytic leukaemia of T-cell type (n = 1) with multiple MBCs clusters, large cell anaplastic lymphoma (n = 1) showing lymphoma cells within multiple MBCs foci, and PTCL of angioimmunoblastic lymphadenopathy (AILD) type (n = 6) with solitary (n = 4) or multifocal (n = 2) MBCs reaction. Progression from AILD-hyperimmune reaction to PTCL of AILD type could be observed in one case by three consecutive follow-up biopsies. While MBCs proliferation associated with hyperimmune reaction was prominent, in PTCL of AILD type only isolated or small multiple clusters of MBCs were present. In PTCL of AILD type, MBCs seemed to be a residual component of a prior hyperimmune reaction diminishing with progress of the disease. Therefore we assume that the development of PTCL of AILD type from preceding hyperimmune reaction is more common than previously considered. Cytologically, MBCs proliferation associated with PTCL shows two cell types, as described in reactive lymphadenopathies: the common type and the large cell type MBCs.