World Health Organization type B2 thymoma with an abundance of Hassall's corpuscles: A case report.

Hassall's corpuscles (HCs) are characteristic components of the medulla of the mammalian thymus and thymoma with an abundance of HCs is even more rare, with only five cases having been reported in the literature, to the best of our knowledge. Furthermore, their morphology usually resembles World Health Organization (WHO) type B2 or B3 thymoma. The biological behavior appears indolent and is rarely associated with myasthenia gravis. However, whether it is a separate entity or a variant of organotypical thymoma WHO B2 or B3 remains to be elucidated. The present case report reports a type B2 thymoma with a large presence of HCs from a 58-year-old Chinese woman, and investigates its histopathological characteristics, immunological features and biological behavior. Notably, the present case appeared biologically more aggressive compared with the cases reported previously. The aim of describing this rare case of thymoma with an abundance of HCs is so that it can be recognized and classified by pathologists.