The focus of this appraisal was on patients with the following subtypes of CTCL: mycosis fungoides (MF; the most common CTCL variant, accounting for around 60% of CTCLs), Sézary syndrome (SS; approximately 2% of CTCLs [3]) and primary cutaneous CD30+ lymphoproliferative disorders (LPDs), comprising primary cutaneous anaplastic large-cell lymphoma (pcALCL) and lymphomatoid papulosis (LyP) (8% and 12% of CTCLs, respectively [3]). This evidence concerns the gene TNFRSF8 and Sezary syndrome.