Epidemiological changes in cutaneous lymphomas: an analysis of 8,593 patients from the French Cutaneous Lymphoma Registry.

BACKGROUND Primary cutaneous lymphomas (PCLs) are a heterogenous group of T- (CTCL) and B-cell (CBCL) malignancies. Little is known about their epidemiology at initial presentation in Europe and about potential changes over time. OBJECTIVES Aim of this retrospective study was to analyse the frequency of PCLs in the French Cutaneous Lymphoma Registry (GFELC) and to describe the demography of patients. PATIENTS AND METHODS Patients with a centrally validated diagnosis of primary PCL, diagnosed between 2005 and 2019, were included. RESULTS Calculated incidence was unprecedently high at 1.06/100,000 person-years. The number of included patients increased yearly. Most PCL subtypes were more frequent in male patients, diagnosed at a median age of 60 years. The relative frequency of rare CTCL remained stable, the proportion of classical mycosis fungoides (MF) decreased, while its variants (e.g. folliculotropic MF) increased. Similar patterns were observed for CBCL, for example the proportion of marginal-zone CBCL increased over time. CONCLUSIONS Changes in PCL frequencies may be explained by the emergence of new diagnostic criteria and better description of the entities in the most recent PCL classification. Moreover, we propose an algorithm to confirm the diagnosis of PCL by central validation of the cases.