HDAC9 and primary cutaneous T-cell non-Hodgkin lymphoma: This is the case of HDAC inhibitors such as valproic acid, vorinostat (suberoylanilide hydroxamic acid, SAHA, Zolinza®), the cinnamic hydroxamic acid analogue panobinostat (LBH589, Farydak®) or belinostat (PXD101, Beleodaq®) (Figure 1) that entered into clinical trials in AML [37,38,39,40] and were approved in other leukemia or hematological diseases such as vorinostat for the treatment of cutaneous T cell lymphoma (CTCL), panobinostat against multiple myeloma or belinostat to treat peripheral T-cell lymphoma [41].