Background Patients undergoing complete resection of thymoma occasionally develop a recurrence of thymoma; they are also at risk of developing a second malignancy. The objective of our study was to compare the incidence and mortality of a second malignancy versus a recurrence of thymoma during the postoperative follow-up period after complete resection of thymoma. Methods A retrospective chart review was performed on our prospectively maintained database to identify patients undergoing complete resection of thymoma at our institution between 1991 and 2016. The incidence and related mortality of a second malignancy or recurrence of thymoma were recorded. Results One hundred and sixty-four patients were identified. Follow-up ranged from 1 to 239 months (median 54 months). During follow-up, 12 patients had a recurrence of thymoma and 14 developed a second malignancy. The mean risk ratio of recurrence to second malignancy was 0.58 (95% confidence interval: 0.48-0.69) at 5 years, 0.58 (95% confidence interval: 0.49-0.68) at 10 years, and 0.51 (95% confidence interval: 0.43-0.60) at 15 years. The mean risk ratio of recurrence versus second malignancy for related death was 0.59 (95% confidence interval: 0.50-0.70) at 5 years and 0.61 (95% confidence interval: 0.52-0.72) at 10 years. Conclusion It appears that patients undergoing complete resection of thymoma have a higher incidence of a second malignancy and a greater related mortality rate than a recurrence of thymoma. A multiinstitutional database is required to more rigorously evaluate both risks and to confirm our results.
Keywords: Incidence; Myasthenia gravis; Neoplasm recurrence; Neoplasms; Thymectomy; Thymoma; local; second primary.