Angioimmunoblastic T-Cell Lymphoma Diagnosed From Serous Effusion by Integration of Cytologic Features and Ancillary Studies

Objectives To explore the approach to the diagnosis of malignant serous effusion (SE) caused by angioimmunoblastic T-cell lymphoma (AITL). Methods The clinical, cytomorphologic, immunophenotypic, and molecular features of 6 patients were summarized. Results Clinically, SE caused by AITL was predominant in middle-aged and older male patients with multiple SEs and lymphadenopathy. Cytomorphology showed small to medium-sized, irregular lymphocytes with clear cytoplasm and mixed with various inflammatory cells and apoptosis. Hodgkin/Reed-Sternberg-like cells were detected in 2 of 6 cases. Furthermore, 2 patterns of cytomorphology were described for the first time. Flow cytometry revealed abnormal T-cell populations with loss of surface CD3 (3/4 cases) and CD7 (3/4 cases). In addition, B-cell populations lacking surface immunoglobulin (Ig) were identified in 2 of 4 cases. Immunocytochemical staining revealed expression of at least 2 T follicular helper markers. Epstein-Barr virus-encoded RNA (EBER)-positive cells were demonstrated in 4 of 5 cases. Clonal T-cell receptor gamma chain rearrangement was detected in 6 cases, and 3 of them had concomitant clonal immunoglobulin gene rearrangement. Moreover, 2 cases revealed discrepant findings regarding IgH/Ig kappa rearrangements in cytohistologic correlation. Conclusions This study broadens the morphologic spectrum of malignant SE caused by AITL and provides diagnostic criteria in routine practice.