Xanthomatous Thymoma: A Clinicopathologic and Immunohistochemical Study of 10 Cases

Objectives: Ten cases of thymomas with an extensive xanthomatous component are presented. Methods: Cases were identified during a review of more than 500 cases of thymomas. Histologic material from surgical resections was evaluated. Results: The patients included five men and five women aged 47 to 64 years who had nonspecific symptoms. Grossly, all tumors were solid, measuring 2.5 to 4.5 cm. Eight tumors were encapsulated; two were minimally invasive. Histologically, the tumors showed varying histologies, all with an extensive xanthomatous component comprising 50% to 80% of the tumor. Immunohistochemical stains showed tumor cells positive for keratin and keratin 5/6 while the xanthomatous component was positive for CD68. Follow-up information showed nine patients remain alive with no recurrence. No follow-up information was obtained in one patient. Conclusions: The presence of an extensive xanthomatous component may pose difficulties in the interpretation of these tumors. This study highlights the importance of proper sampling and awareness of this unusual feature.