Cytotoxic/natural killer cell cutaneous lymphomas. Report of EORTC Cutaneous Lymphoma Task Force Workshop

Primary cutaneous CD8+ and CD56+ T-cell lymphomas express HLA-G and killer-cell inhibitory ligand, ILT2

Primary cutaneous lymphomas constitute a spectrum of diseases characterized by a clonal accumulation of lymphocytes in the skin. Cutaneous T-cell lymphomas of the cytotoxic phenotype, including CD8+ and CD56+ lymphomas, are rare entities that have only been recently recognized and characterized. These lymphomas often show an aggressive clinical course. We investigated the expression of human leukocyte antigen G (HLA-G) and interleukin 10 (IL-10) in conjunction with expression of HLA-G killer-cell inhibitory receptor ligand immunoglobulin-like transcript 2 (ILT2) in 3 CD56+CD4+ and 4 CD8+ cutaneous T-cell lymphomas. HLA-G expression was detected in 2 of 3 lymphomas of the CD56+CD4+ type and in all lymphomas of CD8+ type. It is of note that CD56+CD4+ lymphomas displayed stronger HLA-G reactivity. The expression of IL-10 matched the expression of HLA-G. Together with the expression of IL-10, HLA-G might be one of the factors accounting for the evasion of immunosurveillance, thus contributing to aggressive phenotype of these lymphoma entities.

Recent developments in the biology and therapy of T-cell and natural killer-cell lymphomas

PURPOSE OF REVIEW

T-cell/natural killer (T/NK)-cell lymphomas represent a group of poor-risk lymphoproliferative disorders that have only recently been recognized as distinct clinicopathologic entities. The average outcome with currently available therapy is substantially inferior to that of aggressive B-cell lymphomas. Significant gaps remain in our knowledge of their origin, diagnosis, and clinical spectrum. This review outlines recent developments in the biology and molecular genetics of these disorders, current diagnostic challenges, and future avenues for therapy.

RECENT FINDINGS

Several cancer-prone transgenic mouse models that develop predominantly T/NK-cell lymphomas have been produced in the past 2 to 3 years. These models point to an important role for chronic cytokine stimulation and for disruption of genes involved in the control of chromatin remodeling and maintenance of genome integrity in the pathogenesis of T-cell lymphomas. The recognition of T/NK-cell lymphomas has been greatly facilitated by the broad acceptance of standard diagnostic criteria and by the increasing availability of assays for the analysis of T-cell receptor rearrangement and a more precise definition of functional T/NK-cell subsets. New drugs with potential for use in T/NK-cell lymphomas, including monoclonal antibodies, tyrosine kinase inhibitors, synthetic retinoids, immunoconjugates, and immunosuppressive molecules with novel mechanisms of action are in the early phase of clinical investigation.

SUMMARY

Much remains to be learned in the pathogenesis, clinical spectrum, and optimal therapy of T/NK-cell lymphomas. The availability of animal models of disease, new diagnostic tools, and targeted drugs with novel mechanisms of action should lead to rapid progress in this group of malignancies in the near future.

World Health Organization classification of hematopoietic and lymphoid tissues: implications for dermatology

The new World Health Organization (WHO) classification of hematopoietic and lymphoid malignancy represents the first worldwide consensus document on the classification of lymphoma/leukemia. Its aim is to supercede all existing classification systems, including the Revised European American Classification (REAL), and the organ-based classification of cutaneous lymphoma proposed in 1997 by the European Organization for Research and Treatment of Cancer (EORTC) cutaneous lymphoma project group. This article compares the REAL, EORTC, and WHO classifications with particular reference to cutaneous lymphoma. It identifies those entities that have been adopted from the EORTC classification, and illustrates important new entities in the category of cytotoxic T-/NK-cell lymphomas that characteristically present in the skin or subcutaneous tissue. However, WHO is not an organ-based classification and some categories (eg follicular B-cell lymphoma and peripheral T-cell lymphoma) include both cutaneous and systemic diseases, and these may have very different prognoses. It is, therefore, important that cancer registries are capable of recording sites of involvement for both B- and T-cell lymphomas so that the incidence and prognosis of cutaneous lymphomas can be established from national data sets in future years.