A Case Series: Can a Cytological Smear Indicate the Histological Type of Thymoma and Distinguish Thymoma From Thymic Carcinoma?

Abstract

Introduction

The cytological characteristics of thymoma are not extensively documented in the literature, primarily due to the tumor's rarity. To our knowledge, there are no standardized criteria for the cytological classification of thymomas.

Case Reports

We report three cases of female patients with cytological smears of thymic epithelial neoplasms, correlating them with the corresponding surgical specimens. In all three smears, the cytological features of the cells were similar and consisted of epithelial and lymphocytic components. Epithelial cells were approximately twice the size of lymphocytes, although some were five times larger, displaying prominent nucleoli and marked nuclear atypia. In many areas of the smears, prominent crush artifacts with chromatin streaking were observed in thymoma cases. The thymic carcinoma case had an inconspicuous crush artifact. The number of lymphocytes varied on the smears. In the smears of thymoma, we had a high number of lymphocytes intermixed with epithelial cells, while in thymic carcinoma, we have just a few scattered lymphocytes. In one case of thymoma, a higher number of mast cells were observed.

Conclusion

Preoperative diagnosis of mediastinal masses is essential for the future clinical management of these patients. As such, cytological diagnosis sometimes plays an important role, although the distinct cytological features of thymic epithelial lesions can be challenging. Our cases suggest specific cytological features that may help differentiate thymoma from thymic carcinoma.