Haema 2010; 1(1): 4-10
G. Levidou, P. Korkolopoulou and E. Patsouris
1st Department of Pathology National and Kapodistrian University of Athens, “Laikon”, General Hospital, Athens
T/NK cell neoplasms are uncommon (accounting less than 10% of all non-Hodgkin lymphomas)tumours of mature and immature T or natural killer (NK) cells at various stages of differentiation. Therapy of the T lymphomas has not been so far as successful as of aggressive B-cell lymphomas, and most peripheral T lymphomas (PTLs) have a poor prognosis. The molecular pathogenesis of most PTLs is poorly understood. In the recent WHO classification, clinical features, in conjunction with morphological and immunophenotypic criteria, are used to define most disease entities. Functionally, T-cell lymphomas are related to the two major arms of the immune system, the innate and adaptive immunity. NK cells and T cells of the innate immunity recognize antigen in the absence of MHC and are involved in mucosal immunity. The lymphomas derived from these cells often involve cutaneous and mucosal sites. Many T- and NK-cell lymphomas observed commonly in the paediatric and young adult age group are derived from cells of the innate immune system. The expression of cytotoxic molecules in these lymphomas may strengthen apoptosis of tumor and normal bystander cells. Hepatosplenic Tcell lymphoma, belongs to this category and is a systemic disease derived from functionally immature innate effector cells, most often of γδ T cell origin. In contrast, most nodal T-cell lymphomas belong to the adaptive immune system. Moreover, T cell lymphomas of the adaptive immune system occur primarily in adults. Angioimmunoblastic T-cell lymphoma (AILT), a nodal T cell lymphoma, is mostly likely derived from follicular helper T-cells (TFH), a finding that explains many of its pathological and clinical features. Further studies of these neoplasms are needed to elucidate the functional diversity of their normal counterparts.