Cutaneous manifestations of lymphoma: a clinical guide based on the WHO classification. World Health Organization

Cutaneous lymphomas are a heterogeneous group of lymphomas that show variations in histology, immunophenotype, and prognosis. At the time of presentation, cutaneous lymphomas may be primary or may involve the skin as a secondary site of involvement. Primary cutaneous lymphomas, in many instances, are distinct from morphologically similar lymphomas arising in lymph nodes. Their natural history is often more indolent than nodal lymphomas, and for that reason, they often require different therapeutic approaches. A classification scheme should recognize those lymphomas that are unique to the skin, as well as those arising in other sites. The mode of presentation of a lymphoma is often an indication of underlying biological distinctions. However, organ-specific classification systems undermine communication among medical specialists. The World Health Organization classification of hematopoietic and lymphoid malignancies offers a comprehensive approach and proposes that lymphomas should be viewed as a list of individual diseases and that each disease can be defined by a constellation of morphological, biological, and clinical features. The current review will focus on the spectrum of primary and secondary cutaneous lymphomas, emphasizing those features of importance to the clinical oncologist.