has part has part has_part characteristic of part of has modifier abnormal thymus morphology thymus cyst Thymic cysts are rare mediastinal lesions and are thought to result from the congenital persistence of thymopharyngeal tracts and acquired, progressive cystic degeneration of thymic (Hassall) corpuscles and epithelial reticulum of the thymus; congenital cysts are unilocular, whereas acquired cysts are usually multilocular and result as a consequence of inflammatory processes. thymic cysts thymus cysts presence of one or more fluid-filled spaces lined by epithelium within the thymus thymic cyst MP:0014130 cystic thymus abnormal cyst abnormal cystic thymus