Correct!
5. Metastatic renal cell carcinoma
All of the provided choices are reasonable possibilities for the diagnosis in this patient, although lymphoma typically does not display such extensive vascularity. Given the patient’s prior history, metastatic renal cell malignancy is the most likely diagnosis among the choices provided.
Diagnosis: Metastatic renal cell carcinoma to mediastinum with medial right lung invasion
Discussion
Renal cell carcinoma may metastasize widely, and the potential thoracic manifestations of metastatic renal cell carcinoma are protean. Typical thoracic manifestations of renal cell malignancy include lymphadenopathy, lung nodules, pleural nodules and effusion, and lytic foci within the osseous structures of the thorax. Renal cell carcinoma has a recognized propensity for metastasizing to mediastinal lymph nodes, which may occur in the absence of metastatic disease to the lungs, hilar lymph nodes, pleura, or osseous structures of the thorax (Figure 7).
Figure 7. Thoracic manifestations of renal cell carcinoma: subcarinal without other mediastinal or hilar lymph node enlargement, lung nodules, pleural abnormality, or osseous disease in a 61-year-old woman who provided a history of resection of a “benign” renal lesion in Russia 15 years prior to presentation. Frontal (A) and lateral (B) chest radiography shows a subtle contour abnormality (arrows) only faintly visible on the lateral projection. Unenhanced axial CT (C) and axial T1-weighted (D) and coronal dynamic contrast enhanced MRI (E) images show a solid, enhancing lesion (arrow) in the subcarinal space corresponding to the radiographic abnormality. Bronchoscopic transbronchial biopsy was attempted but did not provide diagnostic tissue. Subsequently, surgical biopsy proved renal cell carcinoma.
Similarly, metastatic renal cell carcinoma may spread to hilar lymph nodes without affecting mediastinal lymph nodes, the lungs, pleura, or osseous structures of the thorax (Figure 8), possibly through retrograde lymphatic flow from the thoracic duct or through the lymphatics within the inferior pulmonary ligament.
Figure 8. Thoracic manifestations of renal cell carcinoma: right hilar without mediastinal lymph node enlargement, lung nodules, pleural abnormality, or osseous disease in a 63-year-old man with a brain lesion thought to represent primary intracranial malignancy. During craniotomy, the surgeon noted a densely hemorrhagic mass thought to be unusual for the presumed glioblastoma and the operation was halted. Frontal chest radiography (A), a pre-operative study whose results were not reviewed prior to surgery, shows enlargement of the right hilum (arrow), suggesting lymphadenopathy. Axial contrast-enhanced thoracic CT (B) confirms right hilar lymphadenopathy (arrow). CT of the abdomen (C) shows a solid, centrally necrotic mass (arrow) representing renal cell carcinoma.
Thoracic metastatic lymphadenopathy due to renal cell carcinoma often results in lymph nodes showing soft tissue attenuation, but occasionally metastatic lymphadenopathy from renal cell carcinoma may show significant hypervascularity (Figure 9A-D). Occasionally internal necrosis within lymph nodes or lung nodules (Figure 9E and F) may be seen.
Figure 9. Thoracic manifestations of renal cell carcinoma: variable vascular patterns. Axial contrast-enhanced thoracic CT (A-D) shows extremely hypervascular mediastinal (arrowhead) and left peribronchial (arrow) lymphadenopathy. Axial contrast-enhanced thoracic CT (E and F) in another patient shows necrotic metastatic lung nodules (arrowheads).
Renal cell carcinoma also has a recognized tendency to cause endobronchial metastases (Figure 10).
Figure 10. Thoracic manifestations of renal cell carcinoma: endobronchial metastases. Axial contrast-enhanced thoracic CT displayed in lung (A-C) and soft tissue (D-F) windows shows a hypervascular endobronchial lesion (arrowheads) arising from the proximal right lower lobe bronchus. Bronchoscopic image (G) shows the metastatic endobronchial lesion.
Metastatic lung nodules are a common manifestation of thoracic metastatic disease from renal cell carcinoma, and occasionally the nodules may be quite large or very small, the latter possibly producing a “miliary” appearance (Figure 11).
Figure 11. Thoracic manifestations of renal cell carcinoma: miliary metastases. Frontal (A) and lateral (B) chest radiography in a patient with metastatic renal cell malignancy shows numerous small circumscribed nodules, consistent with a miliary pattern, found to represent miliary renal cell carcinoma metastases. Axial thoracic CT displayed in lung windows (C) shows numerous small nodules consistent with a miliary pattern. The appearance is relatively non-specific and could be seen with disseminated infection, although the larger nodules, particularly the lingular lesion, are more suggestive of a malignant process.
Finally, renal cell malignancy may cause tumor emboli, possibly as a result of renal vein invasion (Figure 12).
Figure 12. Thoracic manifestations of renal cell carcinoma: endovascular metastases. Axial contrast-enhanced thoracic CT (A-D) in a patient with metastatic renal cell carcinoma shows tumor emboli (arrows) in the right upper lobe artery. A centrally necrotic, peripherally enhancing right hilar metastatic lymph node (arrowheads) is present also.
Metastatic disease developing years following apparent curative resection of a renal malignancy is also a recognized phenomenon in patients with renal cell malignancy.
References