Southern blot analysis (SBA) and polymerase chain reaction (PCR)-based testing for monoclonal T-cell receptor gene rearrangements (TCR-GRs), fluorescence in situ hybridization (FISH) for t(2;5)(p23;q35), in situ hybridization for Epstein-Barr virus-encoded mRNA (EBER-ISH), and SBA for human T-cell lymphotropic virus type I (HTLV-I) provirus integration are the most common molecular techniques used for the diagnosis of primary cutaneous non-mycosis fungoides (MF) T-cell and natural killer (NK)-cell lymphoproliferative disorders.