No abstract

Recent evidence has shown that most nasal lymphomas (NL) are associated with a T-cell phenotype and are thus called nasal T-cell lymphomas (NTCL), but little information is available about the T-cell receptor (TCR) expression. The presence of Epstein-Barr virus (EBV) genome has been recently reported in NTCL in Oriental populations in which NL and EBV-associated tumors are more common and in occasional Occidental cases. This prompted us to investigate lymphoma biopsies from 7 non- Oriental patients with NTCL for the expression of natural killer (NK) and T-cell antigens, including TCR proteins, for the presence of EBV- encoded latent membrane protein (LMP) using immunohistochemistry and for the presence of EBV DNA and Epstein-Barr early region (EBER) RNA using in situ hybridization (ISH). Six cases displayed a CD3-, TCR alpha beta-, TCR gamma delta-, CD2+, CD7+, CD5-, CD4-, CD8-, CD56+ phenotype, suggesting that these tumors may be peripheral T-cell lymphomas (PTCL) with extensive loss of T-cell antigens and expression of the NK-cell (CD56) antigen or, alternatively, NK-cell neoplasias. The remaining case was a gamma delta PTCL, as shown by the CD3+, TCR gamma delta+ phenotype and the biallelic gamma and delta TCR gene rearrangements. Using ISH, EBER RNA transcripts were detected in tumor cells in all cases and EBV DNA was shown in the 6 tested cases. In all cases, tumor cells expressed LMP. These findings support the concept that NTCL constitute a distinct group of lymphomas that, in addition to their peculiar clinical features, exhibit an unusual TCR “silent” CD56+ or TCR gamma delta+ phenotype and harbor the EBV. In view of the LMP transforming potential, these data suggest that EBV may play a role in the pathogenesis of NTCL.

Lymphomas with T‐cell phenotype represent a heterogeneous group of diseases differing in histopathology, tumour site, and cell origin. They include peripheral T‐cell lymphomas (PTCLs) derived from αβ cells, but also some recently recognized entities such as γδ hepatosplenic lymphomas and natural killer (NK) cell lymphomas. Only a few studies have investigated the possibility that at least some PTCLs could be derived from lymphocytes with cytotoxic potential. In order to investigate this possibility, 60 cases of PTCL, including 27 cases expressing the αβ T‐cell receptor (TCRαβ), 15 TCRγδ cases and 18 cases expressing neither TCR (TCR silent), as well as 14 cases of NK‐cell lymphomas, were studied by immunohistochemistry for the expression of TIA‐1, perforin, and granzyme B proteins. Expression of TIA‐1 is characteristic of cytotoxic cells regardless of their activation status, whereas expression of perforin and granzymes is highly increased in activated cytotoxic cells and correlates with the induction of cytolytic activity. All NK‐cell lymphomas (11 sinonasal, three systemic cases) expressed TIA‐1, perforin, and granzyme B in most tumour cells. All γδ PTCLs (15 cases) expressed TIA‐1 protein in most tumour cells, with a different cytotoxic antigen profile in hepatosplenic γδ PTCL (TIA‐1+, perforin−, granzyme B−) and in non‐hepatosplenic γδ PTCLs (three nasal, one skin, one lung), the latter expressing the three cytotoxic proteins. Of the 45 cases of αβ and TCR silent PTCL, 15 (33 per cent) were considered to be derived from cytotoxic lymphocytes with expression of at least one cytotoxic protein (TIA‐1, 15/45; perforin, 10/41; granzyme B, 14/38) in tumour cells. This cytotoxic protein expression appeared to be related to the site of localization, since 7/13 (54 per cent) extranodal and only 8/32 (25 per cent) nodal αβ and TCR silent PTCLs expressed TIA‐1, and to histology, since this pattern was observed in a proportion of anaplastic (6/8, 75 per cent) and pleomorphic (8/17, 47 per cent) lymphomas, but not in AILD‐type NHL (0/16). Taken together, our data suggest that NK‐cell lymphomas and non‐hepatosplenic γδ PTCLs represent tumours of activated cytotoxic NK cells and γδ T cells, respectively; that hepatosplenic γδ PTCLs represent tumours of non‐activated cytotoxic γδ T cells; and that a small proportion of αβ and TCR silent PTCLs, mostly extranodal cases, or nodal anaplastic lymphomas, represent tumours of cytotoxic T cells. © 1997 John Wiley & Sons, Ltd.

Non-Hodgkin's lymphomas are divided into B- and T-cell neoplasms. The existence and the clinical relevance of lymphomas derived from the third lymphocyte lineage, ie, natural killer (NK) cells are still controversial. NK cells are lymphocytes that mediate cytotoxicity without prior sensitization. NK cells also have phenotypic and genotypic characteristics: they express the NK-related antigen CD56, T- cell markers such as CD2 and CD7, but do not express CD5 and T-cell receptor (TCR) proteins, and their TCR locus is not rearranged. Therefore, if NK cell lymphomas exist, they should express some T-cell markers, but not alpha beta or gamma delta TCR proteins. Such lymphomas are actually called TCR silent peripheral T cell lymphomas (PTCL). To detect and characterize NK cell lymphomas, we investigated the immunophenotype and immunogenotype of 35 patients with TCR silent PTCL. The first group included 16 patients with a lymphoma of CD5-CD56+ phenotype, which is identical to normal NK cells. These patients had either a nasal/nasopharyngeal lymphoma (11 cases) or a lymphoma with predominant non-nasal/non-nodal initial involvement (five cases). Eight of the nine cases for which immunogenotypic data were available lacked clonal rearrangement of the TCR gamma genes. Thus, these tumors are likely to be NK cell lymphomas. The second group of 15 cases had a CD5+ phenotype (14 were CD56-, and 1 was CD56+) and clonal rearrangement of TCR gamma genes, indicating that they were true PTCL with unproductive TCR rearrangement. The four remaining cases were CD5- CD56- lymphomas and disclosed either a clonal (two cases) or no clonal (two cases) rearrangements of the TCR gamma genes. Altogether these findings show that CD5-CD56+ so-called “TCR silent PTCL” bear the immunophenotype and immunogenotype of normal NK cells and display peculiar clinical features distinct from true PTCL.

This study investigated the combined immunoexpression of p53, p21, bcl-2, bax, Rb and Ki67 proteins in colorectal adenocarcinomas and correlated expression patterns with tumour stage and grade. Paraffin sections from 98 cases of colorectal adenocarcinomas were stained by immunohistochemistry for p53, p21, bcl-2, bax, Rb and MIB-1 (Ki67) proteins. In addition, 12 cases of colorectal adenomas and normal colorectal mucosa were studied in parallel. P53, p21, bcl-2, bax, Rb and Ki67 proteins were detected in at least 5% of tumour cells in 63/98, 72/98, 52/98, 96/98 and 98/98 adenocarcinomas, respectively. Comparative study of the normal-adenoma-carcinoma tissues revealed abrogation of the normal immunotopography in adenomas and adenocarcinomas, and considerable modifications, increase or reduction, of the expression of p53, p21, bcl-2, bax, Rb and Ki67 proteins in adenocarcinomas when compared with normal mucosa and adenomas. Statistically significant correlations were found between low bax expression and Dukes C stage of carcinomas, Ki67 expression and carcinoma grade, and Ki67 and Rb expression. P53, p21, bcl-2 and Rb immunoexpression did not correlate with tumour stage or grade. Our findings show that low bax immunoexpression is frequently related to colorectal adenocarcinomas with lymph node metastases suggesting that low levels of bax expression play a role in late stage colorectal cancer. The correlation between Ki67 and Rb expression, in view of previous data that the hyperphosphorylated inactive Rb protein is frequently increased in colorectal adenocarcinomas, suggests that Rb protein is somewhat ineffective in inhibiting the cell-cycle progression in these malignancies. Furthermore, our findings provide immunohistochemical evidence that the abrogation of the normal immunotopography and the modifications of the expression of p53, p21, bcl-2, bax, Rb and Ki67 proteins reflect important events in colorectal oncogenesis.