CLONAL REARRANGEMENT OF THE T-CELL RECEPTOR BETA-CHAIN GENE IN THE PLEURAL FLUID OF A PATIENT WITH THYMOMA

Thymoma is generally considered as an epithelial malignancy surrounded by lymphocytes not belonging to the tumour. This report documents a c ase of malignant thymoma associated with a lymphocytic pleural effusio n. The pleural lymphocytes were mature T-cells, a small proportion of which were shown to have a monoclonal rearrangement of the beta-chain of the T-cell receptor. On the contrary, the lymphocytes of peripheral blood exhibited a germline configuration. The nature of the monoclona l population found in the pleural fluid is discussed and if the cells are of thymic origin their clonal configuration may point to a neoplas tic nature of lymphocytes infiltrating malignant thymoma. Alternativel y, he clonal T-cell subpopulation may result from an aberrant immunolo gical response to the thymoma.