Thymic epithelial tumours: histopathological classification and differential diagnosis

The epithelial and lymphoid compartments of the thymus can give rise to a wide variety of tumours, including thymomas, thymic carcinomas, lymphoreticular proliferations, germ cell tumours, and sarcomas. While some of these have close similarity to their counterparts in other organs, both in terms of histology and immunohistochemistry, as well as molecular features, others are unique to the thymus. I will discuss the epithelial tumours that can develop in the thymus in this review, with a particular emphasis on resolving differential diagnosis by means of morphology, immunohistochemical profiles, and molecular diagnostics. In this review, the various subtypes of thymic epithelial tumours are described, with attention to differential diagnosis and ancillary techniques, as well as limitations of biopsy and frozen section diagnosis, and the clinical relevance for prognosis and treatment.image