EORTC classification for primary cutaneous lymphomas: a proposal from the Cutaneous Lymphoma Study Group of the European Organization for Research and Treatment of Cancer.

Primary cutaneous lymphomas represent a heterogeneous group of T- and B-cell lymphomas that show considerable variation in histology, phenotype, and prognosis. Recently, the European Organization for Research and Treatment of Cancer (EORTC) Cutaneous Lymphoma Project Group has reached consensus on a new classification for this group of diseases. The EORTC classification for primary cutaneous lymphomas is based on a combination of clinical, histologic, and immunophenotypic criteria, and thus contains well-defined disease entities rather than histologic subgroups. In addition, this new classification contains a number of provisional entities, which may display characteristic histologic features, but are not yet well defined clinically. These provisional entities account for less than 5% of all primary cutaneous lymphomas. In this report the basic principles of this new classification, as well as the characteristic features of the different disease entities, are described. In addition, survival data of 626 patients with primary cutaneous lymphomas derived from the registry of the Dutch Cutaneous Lymphoma Working Group, illustrating the clinical validity of this new classification, are presented.