[The usefulness of induction chemotherapy in cases with tumors showing border-line pathological aspects between thymoma and thymic carcinoma].

We present 2 surgically treated cases with thymoma classified as Masaoka stage III and IV a (type B 3 thymoma), which showed the border-line pathological aspects between the thymoma and thymic carcinoma. Induction chemotherapy [CAV-PVP (cyclophosphamide, adriamycin, vincristine sulfate, etoposide) therapy in one case and ADOC (adriamycin, cisplatin, vincristine sulfate, cyclophosphamide) therapy in another case] preluded their surgical resection resulted in reduction of the tumor's size moderately or severely. After achievement of induction chemotherapy, these tumors were resected with the midsternotomy approach, along with resection of the right upper lobe and the left brachiocephalic vein replacing the expanded pdytetrafluoroethylene (ePTFE) graft following mediastinal lymphnodes dissection in one case and leaving the tumor tissue around the pulmonary trunk in another case. Postoperative irradiation of 40 Gy in one case and 60 Gy in another case were performed in the mediastinal regions. From pathological aspects especially in second case, though the specimen by preoperative needle biopsy stained positive for bcl-2 and strong immunoreactivity (20%) for MIB-1, specimens excised operatively after induction chemotherapy showed negative staining for bcl-2 and little staining (lower than 5%) for MIB-1. This fact indicates that the induction chemotherapy makes the tumor less malignant, in other words, from the face of thymic carcinoma to the face of thymoma. Induction chemotherapy performed for the purpose of reducing the tumor size was very advantage in these 2 cases with type B 3 thymoma.