[Clonal rearrangement of intratumoral T-cell receptor beta-chain gene in two patients with thymoma accompanied by pure red cell aplasia].

We encountered two cases of thymoma accompanied by pure red cell aplasia and demonstrating clonal rearrangement of the T-cell receptor beta-chain gene (TCR-beta) in lymphocytes. Patient 1 was a 55-year-old man and Patient 2 was a 43-year-old woman. Both had severe anemia and mediastinal tumors. Bone marrow aspiration was performed and pure red cell aplasia diagnosed. Thymoma was the presumptive diagnosis for the mediastinal tumors, and extended thymectomy was performed. The post-operative diagnosis was invasive thymoma (spindle-cell type) in Patient 1 and non-invasive thymoma (mixed lympho-epithelial type) in Patient 2. The cell compositions (%) obtained with T-cell surface marker analysis were as follows: [table: see text] Southern blot analysis disclosed clonal rearrangement of TCR-beta genes in thymoma thymocytes from both patients.