XV. Primary cutaneous lymphomas

Abstract

Primary cutaneous lymphomas (PCLs) are defined as non-Hodgkin lymphomas that present in the skin with no evidence of extracutaneous disease at the time of diagnosis. After the gastrointestinal lymphomas, PCL are the second most common group of extranodal non-Hodgkin lymphomas with an estimated annual incidence of 1/100 000. These PCLs must be distinguished from nodal or systemic malignant lymphomas involving the skin secondarily, which often have another clinical behavior, have a different prognosis and require a different therapeutic approach. In recent lymphoma classifications (WHO-EORTC; WHO 2008) the different types of primary cutaneous T-cell lymphoma (CTCL) and primary cutaneous B-cell lymphoma (CBCL) are therefore included as separate entities (see Table 1) [1, 2]. In the western world, CTCL constitutes 75%–80% of all PCLs and CBCL 20%–25%, but different distributions have been observed in other parts of the world. Within the group of CTCLs roughly three categories can be distinguished: (i) the group of classical CTCLs, including mycosis fungoides (MF), variants or subtypes of MF and Sezary syndrome (SS); (ii) the group of primary cutaneous CD30-positive lymphoproliferative disorders (CD30+ LPD); and (iii) a group of rare often aggressive cutaneous T/NK-cell lymphomas, including subcutaneous panniculitis-like T-cell lymphoma (SPTCL), extranodal NK/T-cell lymphoma, nasal type, and primary cutaneous peripheral T-cell lymphoma, not otherwise specified (PTCLNOS). Well-defined types of CBCL include primary cutaneous marginal zone lymphoma (PCMZL), primary cutaneous follicle center lymphoma (PCFCL) and primary cutaneous diffuse large B-cell lymphoma, leg type (PCLBCL, LT). Herein, characteristic features of the main types of CTCL and CBCL are summarized and recent observations regarding diagnosis, prognostic factors and treatment are described.