The thymus.
D006801:Humans; D013945:Thymoma / Q000473:pathology; D013950:Thymus Gland / Q000002:abnormalities / Q000473:pathology* / Q000502:physiology; D013952:Thymus Hyperplasia / Q000473:pathology; D013953:Thymus Neoplasms / Q000473:pathology