A phenotypic and genotypic study of three node-based, low-grade peripheral T-cell lymphomas: Angioimmunoblastic lymphoma, T-zone lymphoma, and lymphoepithelioid lymphoma

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Abstract
Phenotypic and genotypic findings were correlated and compared for 35 specimens taken from 34 patients with three specific types of low‐grade peripheral T‐cell lymphoma: lymphoepithelioid (LeL), angioimmunoblastic (AILD), and T‐zone (TzL) lymphoma. Frozen sections were stained by the double immunoenzymatic method using a combination of the monoclonal antibody Ki‐67 for proliferating nuclei and those against lymphocyte surface antigens. Data were correlated by observing clonal rearrangements in the genes of the T‐cell receptor beta chain (TCRβ). Of the 35 specimens studied, 32 (91%) were of predominantly CD4+ helper cell proliferation, and 21 (60%) showed the TCRβ gene rearrangement. There were 15 cases of AILD and TzL with predominantly helper cell proliferation, which contained a minimum of 21% CD4+Ki‐67+ cells based on the total number of cells present in the specimen. Of these, 13 (87%) showed TCRβ rearrangement. In eight cases, containing a maximum of 20% CD4+Ki‐67+ cells, only one (13%) showed any rearrangement. In addition, TCRβ rearrangement was observed in five of the nine cases of LeL, including two cases with only 12% CD4+Ki‐67+ cells. For each of the three types, the proportion of CD4+ cells among the Ki‐67+ population showed a relatively good correlation with the clonal TCRB gene rearrangement. Moreover, there was a significant difference (P < 0.05) in survival curves between groups with and without TCRP rearrangement, although no obvious plateau was seen. These results suggest that the paucity of tumor cells in these lesions may account for the absence of a detectable band of rearrangements in some patients with one of these three specific types of low‐grade peripheral T‐cell lymphoma.