Mediastinal metastases of infradiaphragmatic malignancies

Mediastinal lymph node metastases from infradiaphragmatic malignancies are reported to be a rare occurrence. The results of previous studies have been based on the evaluation of chest radiographs. In this study we retrospectively reviewed the chest and abdominal computed tomography examinations of 50 such patients. Of these, 25 had renal cell carcinoma and the remainder, other genitourinary or gastrointestinal carcinomas. The major nodal groups involved in the mediastinum were the right paratracheal in 41 cases, subcarinal in 31, paraesophageal in 26, and aortopulmonary in 25. Hilar nodes were involved in 21 cases. In the abdomen, para-aortic and or retrocrural adenopathy was present in 29 cases. Of 21 patients with pulmonary metastases, only 12 cases were associated with ipsilateral hilar lymphadenopathy. Supraclavicular lymphadenopathy occurred in only 8 patients. These results suggest that spread of infradiaphragmatic malignancies to the mediastinum occurs primarily by extension from the retrocrural and para-aortic nodes into the thoracic duct and then by antegrade flow in the thoracic duct and its collaterals, with retrograde flow from these channels to the mediastinal nodes.