Cutaneous lymphomas: A proposal for a unified approach to classification using the R.E.A.L./WHO Classification

Abstract

The classification of cutaneous lymphomas has been controversial. The EORTC has proposed that conventional classification schemes are not suitable for cutaneous lymphomas, and that a unique classification system is required. The authors review the suitability of the R.E.A.L. Classification for cutaneous lymphomas, and compare it with the newly proposed EORTC system. The principles of the R.E.A.L. Classification have been adopted by the WHO committees for the classification of hematopoietic and lymphoid neoplasms. Each disease is defined as a distinct entity based on an integration of morphology, immunophenotypic and genetic features, clinical presentation and course, and normal cellular counterpart. If either primary or secondary involvement of the skin is a constant factor, this aspect is considered integral to disease definition. Organ-specific classification schemes may impede the recognition of common features of diseases involving multiple anatomic sites. For example, cutaneous marginal zone B-cell lymphomas (formerly designated cutaneous immunocytomas) mirror the features of MALT lymphomas in other anatomic sites. While the EORTC Classification for cutaneous lymphomas attempts to emphasize certain aspects of these neoplasms of importance to dermatologists, the use of multiple classification systems is a step backward, and may lead to confusion among hematologists/oncologists, and dermatologists. Nevertheless, cutaneous lymphomas often have a more indolent natural history than nodal lymphomas, and may require different therapeutic approaches. Clinical features are an important prognostic factor and should be utilized in guiding therapy. For cutaneous lymphomas the presence or absence of systemic spread is particularly important. Additionally, the site of origin is often important in the definition of disease entities. Organ-specific classification schemes, such as the EORTC Classification for cutaneous lymphomas, are not required, and indeed may impede the recognition of common features of diseases involving multiple anatomic sites. A common classification system, such as the R.E.A.L./WHO Classification, should be utilized for all lymphomas, regardless of the site of origin.