A clinicopathologic study of node-based, low-grade, peripheral T-cell lymphoma. Angioimmunoblastic lymphoma, T-zone lymphoma, and lymphoepithelioid lymphoma.

Postthymic (peripheral) T-cell malignancy shows marked diversity in histopathologic appearances as well as in clinical and prognostic aspects. Histologic findings and clinical behavior of 110 cases of the three specific types of low-grade, peripheral T-cell lymphomas, i.e., lymphoepithelioid (LeL), angioimmunoblastic (AILD), and T-zone (TzL) lymphomas, were studied. There were 74 men and 36 women (age range, 24 to 90 years; median, 58). Histologic study of LeL, AILD, and TzL showed prominent reactive features which are distinct from those of high-grade, T-cell lymphomas (pleomorphic/immunoblastic types). Corresponding to the differences in the histologic pictures of each type, there were differences in the clinical pictures and prognosis. Hypergammablobulinemia (greater than 4 g/dl) was more common in AILD than in the others. However, these three types exhibited a widely variegated, sometimes overlapping spectrum of histologic appearances, and it was extremely difficult to distinguish one from the other on several occasions. The same was true of their clinical and laboratory findings, and they had a relatively favorable prognosis as compared with pleomorphic/immunoblastic lymphomas. Although the conventional phenotypic analysis showed the prominent mixture of helper/inducer and cytotoxic/suppressor T-cells with a varying degree of B-cells and histiocytes, the double immunohistochemical study revealed that the neoplastic cells consisted predominantly of helper/inducer cells. Furthermore, five cases (5%) showed the morphologic transition among the three types or development into pleomorphic/immunoblastic lymphoma. They seemed to constitute a comprehensive and yet distinct group of T-cell lymphomas. Based on morphologic findings and clinical data, the authors demonstrated the distinct character of the node-based, low-grade, T-cell lymphomas and also the relationship among the three types in this group. The results of phenotypic and genotypic analyses also support the concept proposed here.