RESUMO
<p><b>BACKGROUND</b>Extranodal natural killer/T-cell (NK/T cell) lymphoma, nasal-type, is a rare lymphoma. Skin is the second most common site of involvement after the nasal cavity/nasalpharynx. The aim of this study was to investigate the clinicopathologic features, immunophenotype, T cell receptor (TCR) gene rearrangement, the association with Epstein-Barr virus (EBV) infection and p53 gene mutations of the lymphoma.</p><p><b>METHODS</b>The clinicopathologic analysis, immunohistochemistry, in situ hybridization for EBER1/2, TCR gene rearrangement by polymerase chain reaction (PCR), mutations of p53 gene analyzed by PCR and sequence analysis were employed in this study.</p><p><b>RESULTS</b>In the 19 cases, the tumor primarily involved the dermis and subcutaneous layer. Immunohistochemical staining showed that most of the cases expressed CD45RO, CD56, CD3ε, TIA-1 and GrB. Three cases were positive for CD3 and two cases were positive for CD30. Monoclonal TCRγ gene rearrangement was found in 7 of 18 cases. The positive rate of EBER1/2 was 100%. No p53 gene mutation was detected on the exon 4 - 9 in the 18 cases. Fifteen cases showed Pro (proline)/Arg (arginine) single nucleotide polymorphisms (SNPs) on the exon 4 at codon 72. The expression of p53 protein was 72% (13/18) immunohistochemically.</p><p><b>CONCLUSIONS</b>Cutaneous NK/T-cell lymphoma is a rare but highly aggressive lymphoma with poor prognosis. No p53 gene mutation was detected on the exon 4 - 9, and Pro/Arg SNPs on p53 codon 72 were detected in the cutaneous NK/T-cell lymphoma. The overexpression of p53 protein may not be the result of p53 gene mutation.</p>