The Impact of Neoadjuvant Chemotherapy on the Histopathological Assessment of Thymomas: A Clinicopathological Correlation of 28 Cases Treated with a Similar Regimen

Twenty-eight patients treated with neoadjuvant chemotherapy for invasive thymoma are presented. The patients were 16 men and 12 women between the ages of 23 and 75 years (mean = 50.8 years). All patients were treated with a similar modality consisting of three courses of cyclophosphamide, doxorubicin, cisplatin, and prednisone prior to their surgical resection. Grossly, all tumors were ill-defined invasive masses ranging in size from 5 to 18 cm in greatest dimension. Histological evaluation of the resected tumors showed a gamut of histological features, including necrosis, cystic changes, hemorrhage, histiocytic proliferation, calcifications, and cholesterol cleft granulomas in varying proportions. In addition, we found that some histological types of thymoma appeared to be affected less by neoadjuvant chemotherapy, while others, mainly those tumors with a more prominent lymphocytic component, showed more extensive histological changes. Based on the results of this study, it appears that the response to induction chemotherapy in thymomas may be determined by the histological characteristics of the tumor, with treatment-related changes being present predominantly in cases in which the tumor had a prominent lymphocytic component (WHO type B1 and B2), while tumor viability was highest in cases where the histological type corresponded to spindle cell and atypical thymomas (WHO types A and B3, respectively). In addition, it has to be noted that the histological changes attributed to treatment effect may also be seen in untreated tumors thereby not allowing for definitive separation of treated from nontreated thymomas.