Synchronous independent bifocal orthotopic thymomas. A case report.

A case of synchronous multiple thymomas is reported. The patient was an 81-year-old woman with 2 separate thymomas in the anterior mediastinum. A histological study revealed that both thymomas consisted of dense lymphocyte infiltration in the stroma and a small number of polygonal epithelial tumor cells with clear nuclei and distinct nucleoli. Immunohistochemical staining using the antibodies to 2 antigens, bcl-2, and MIB-1 showed identical staining patterns. In spite of these findings, we considered their origin to be synchronous multicentric development rather than intra-thymic metastasis, based on the non-invasive nature of these tumors.