The new World Health Organization–European Organization for Research and Treatment of Cancer classification for cutaneous lymphomas: a practical marriage of two giants

Summary Following consensus meetings of the two parent organizations, a new World Health Organization–European Organization for Research and Treatment of Cancer (WHO–EORTC) classification for primary cutaneous lymphomas has recently been published. This important development will now end the ongoing debate as to which of these was the preferred classification. The new classification will facilitate more uniformity in diagnosis, management and treatment of cutaneous lymphomas. In particular, it provides a useful distinction between indolent and more aggressive types of primary cutaneous lymphoma and provides practical advice on preferred management and treatment regimens. This will thereby prevent patients receiving high‐grade treatment for low‐grade biological disease. This review focuses on those diseases which have found new consensus agreement compared with the original WHO and EORTC classifications. In cutaneous T‐cell lymphomas, these include folliculotropic mycosis fungoides, defining features of Sézary syndrome, primary cutaneous CD30+ lymphoproliferative disorders (primary cutaneous anaplastic large cell lymphoma, lymphomatoid papulosis and borderline lesions) and subcutaneous panniculitis‐like T‐cell lymphoma. Primary cutaneous CD4+ small/medium‐sized pleomorphic T‐cell lymphoma, primary cutaneous aggressive epidermotropic CD8+ T‐cell lymphoma and cutaneous γ/δ T‐cell lymphoma are allocated provisional entry status and thereby afford better definitions for some cases of currently unspecified primary cutaneous peripheral T‐cell lymphoma. In cutaneous B‐cell lymphomas, diseases which have found new consensus agreement include primary cutaneous marginal zone B‐cell lymphoma, primary cutaneous follicular centre lymphoma, primary cutaneous diffuse large B‐cell lymphoma, leg type and primary cutaneous diffuse large B‐cell lymphoma, other. CD4+/CD56+ haematodermic neoplasm (early plasmacytoid dendritic cell leukaemia/lymphoma) now appears as a precursor haematological neoplasm and replaces the previous terminology of blastic NK‐cell lymphoma. Other haematopoietic and lymphoid tumours involving the skin, as part of systemic disease, will appear in the forthcoming WHO publication Tumours of the Skin . The new classification raises interesting new problems and questions about primary cutaneous lymphoma and some of these are discussed in this article. It is, however, a splendid signpost indicating the direction in which research in cutaneous lymphoma needs to go. In the interim, we have an international consensus classification which is clinically meaningful.