Using fluorescent in situ hybridization analysis, A20 deletions were identified in 4 of 13 samples from patients with pyothorax-associated lymphoma (PAL) (31%), 3 of 20 samples from nasal-type NK/T cell lymphomas (NKTLs) (15%), 1 of 8 samples of EBV-positive DLBCL of the elderly (DLBCL-e) (13%), but not in any of the 11 samples from individuals with methotrexate-related lymphoproliferative disorder (MTX-LPD) (0%). Here, TNFAIP3 is linked to extranodal nasal NK/T cell lymphoma.