Thymic epithelial tumors represent the most common neoplasms of the anterior mediastinum, while atypical type A thymoma is a rare subtype of thymoma. On the morphological basis of type A thymoma, this tumor exhibits some atypical histological features, such as abundant cells, increased mitotic counts, tumor necrosis, and increased Ki67 index. At present, the clinical and pathological data of this tumor is still available. Since it was formally named, 16 cases have been reported around the world. In order to improve the understanding of the disease, this article reviews the related literature and tries to elaborate the atypical type A thymoma from the aspects of pathological features, clinical manifestations, epidemiology and differential diagnosis.