Novel association between thymomas and T-cell Non-Hodgkin's lymphomas: Evaluation of 5 cases

Abstract

7326 Background: Thymomas are often accompanied by a variety of paraneoplastic syndromes and have been associated with abnormal intra-thymic T-cell development, as well as oligoclonal T-cell populations in the bone marrow of certain patients. Prior series have shown an increased incidence of secondary malignancies in patients with thymoma. Recently, Engels et al. (Int. J. Cancer: 105, 546–551) demonstrated an excessive occurrence of Non-Hodgkin's lymphomas (NHL) after a thymoma diagnosis, identifying 7 cases among 9 SEER registries; however, only B-cell NHL cases were found. We report the association between thymomas and T-cell NHLs and examine its possible causal relationship to abnormal T-cell maturation within the thymus, employing immunohistochemical stains and assessment of T-cell clonality. Methods: Five patients with thymoma and T-cell NHL (both biopsy-proven) were identified through the Thymoma Clinic database at Indiana University. The T-NHL diagnosis could precede, concur or be subsequent to the thymoma. Original thymic samples are being stained for CD2, CD3, CD5, CD4, CD8, CD25, CDK6, p53 and compared to NHL samples. Thymic T-lymphocytes and original T-NHL lymphocytes are being subjected to T-cell receptor gene rearrangement studies by PCR. Results: Median age at the time of thymoma diagnosis was 38 years (range, 28–56). Patient characteristics are summarized in the table. All patients had cortical thymoma. Two patients (cases 4 and 5) presented with the T-NHL in the setting of persistent thymoma. Conclusions: We describe a novel clinical association between thymomas and T-cell NHLs. Abnormal T-cell maturation induced by thymomas may play a role in T-NHL pathogenesis in these patients. Correlative studies will be available for presentation at the time of the Annual Meeting. No significant financial relationships to disclose.