Ossifying thymoma clinically presenting with peripheral T-cell lymphocytosis.

We believe there has been only one ossifying thymoma reported in the English literature. We herein reported another such case with additional peculiar presentation of peripheral T-cell lymphocytosis. A 62-year-old woman was incidentally found to have an anterior mediastinal tumor during a medical check-up, which was surgically resected 42 months later and histopathologically confirmed to be a type B1 thymoma with stromal ossification. Fifty months after tumor removal, this patient remains alive and well without relapsed disease.