Abstract: Abstract: Purpose To investigate clinicopathological features of thymoma with spontaneous regression including extensive hemorrhage, necrosis and cystic changes, so as to deepen the understanding of this entity type of thymoma. Methods clinicopathological features of two cases of thymomas with extensive hemorrhage, necrosis and cystic changes were analyzed and discussed combing related literature. Results The prognosis of two cases were both good with follow-up time 28 months and 6 months respectively, one case is a female patient, 61 years old with B2 thymoma , Masaoka stage III, and the other case is a male patient, 65 years old with B2 thymoma, Masaoka stage I. Conclusions This entity of thymoma with extensive hemorrhage, necrosis and cystic changes may have inert biological behavior, but the more clinic data and prolonging follow-up time were needed to evaluate the prognosis of these patients.

Key words: thymoma, spontaneous regression, hemorrhage, necrosis, cystic change