Three cases of immunoblastic lymphadenopathy (IBL)‐like T‐cell lymphoma were analyzed immunologically, and the ultrastructure of mononuclear cells in the lymph nodes and peripheral blood was examined. In the peripheral blood, light microscopic examination revealed vacuolated lymphocytes. These vacuolated lymphocytes formed rosettes with sheep erythrocytes, and they were CD3‐ and CD4‐positive using the avidin‐biotin method in cases 1 and 2. Electron microscopic examination revealed two kinds of abnormal lymphocytes. One kind was of B‐cell nature with rich lamellated rough‐surfaced endoplasmic reticulum and mitochondria. The other kind had a large cytoplasm, in which Golgi apparatus, some endoplasmic reticulum, some mitochondria and a few vacuoles were seen. Some of these vacuoles had remnants of mitochondrial cristae or were enlarged endoplasmic reticulum. The vacuolated T lymphocytes and activated lymphocytes of B‐cell nature disappeared with chemotherapy but reappeared with relapse of the disease. These observations suggest that vacuolated cells are related to pale cells in lymph node sections. In other words when these vacuolated cells are found in the peripheral blood of patients with lymphoid malignancies, IBL‐like T‐cell lymphoma can be suspected. Copyright © 1990, Wiley Blackwell. All rights reserved
