Histological and immunophenotypic profile of nasal NK T cell lymphomas from Peru: High prevalence of p53 overexpression

Nasal NK/T-cell lymphoma is a unique form of lymphoma highly associated wit h Epstein-Barr virus (EBV). These lymphomas are rare in Western populations and much more prevalent in some Asian and Latin American countries. Althou gh there are several sizable studies from Asian countries, the same is not true from South America. The aim of this study was to analyze a series of 3 2 cases of nasal T-cell lymphoma from Peru and to further extend the charac terization of this disease. Immunohistochemistry was performed on paraffin sections using the following antibodies: CD20 (L26), CD45RO, CD3, Ki67, CD5 7, CD56, TIA-1, bcl-2, and p53. The presence of EBV was investigated with i mmunohistochemical analysis for latent membrane protein (LMP)-1 and in situ hybridization using an antisense riboprobe to EBER 1. The 32 patients incl uded 18 men and 14 women (M:F ratio, 1.2:1), with a median age of 43 years (11 to 72). Three categories were identified: (1) Nasal NK/T cell lymphomas (28 cases): The morphology ranged from small or medium-sized cells to larg e transformed cells. Necrosis was present in 86% of the cases, and angioinv asion was seen in 36% of the cases. All cases were positive for CD45RO, CD3 , and for TIA-1. CD56 was positive in 21 of 27 cases (78%), and CD57 was ne gative in all cases. EBER 1 positivity was identified in most of the tumor cells in 27 of 28 cases (96%), including the six cases in which CD56 was ne gative. Overexpression of p53 was detected in 24 cases (86%). (2) Blastic N K cell lymphoma (1 case): The neoplastic cells resembled those of lymphobla stic lymphoma. CD56 and CD45RO were positive; TIA-1, TdT, and EBER-1 were n egative. (3) Peripheral T-cell lymphoma (PTCL) unspecified (3 cases): CD56, TIA-1, and EBER-1 were negative. Nasal lymphomas from Peru with a T cell p henotype are predominantly EBV-associated NK/T cell lymphomas, similar to t hose described in Asian countries. The expression of CD56, TIA-1, and EBER- 1, in combination, are very useful markers for the diagnosis of nasal NK/T cell lymphoma in paraffin-embedded tissue. The differential diagnosis of T- cell lymphomas in the nasal region should include rare cases of PTCL unspec ified and the blastic variant of NK cell lymphoma. P53 is overexpressed in 86% of the cases. The significance of this finding with regard to clinical behavior and prognosis remains to be determined. This is a US government wo rk. There are no restrictions on its use.