Other Respiratory and Intrathoracic Organs

T-C39 designates malignant neoplasms arising in other and unspecified parts of the respiratory system and intrathoracic organs, encompassing sites such as the mediastinum, pleura, and other respiratory structures not covered by more specific topography codes. It is used when a tumor's origin cannot be assigned to a defined organ like lung, trachea, or bronchus.