Romidepsin (Istodax), a histone deacetylase (HDAC) inhibitor, was approved by the US Food and Drug Administration (FDA) in November 2009 for the treatment of cutaneous T-cell lymphoma (CTCL) in patients who have received at least one prior systemic therapy and in May 2011 for the treatment of PTCL in patients who have received at least one prior therapy (Celgene Corporation, 2014). This evidence concerns the gene HDAC9 and primary cutaneous T-cell non-Hodgkin lymphoma.