HDAC9 and primary cutaneous T-cell non-Hodgkin lymphoma: Vorinostat is the first HDAC inhibitor approved for the treatment of cancer: in October 2006, the US Food and Drug Administration granted approval to vorinostat for the treatment of cutaneous manifestations of cutaneous T-cell lymphoma (CTCL) in patients with progressive, persistent or recurrent disease on or following two systemic therapies [12].