Prognostic implications of the magnetic resonance imaging appearance in papillary renal cell carcinoma

Objective: To evaluate the prognostic implications of the MRI appearance and pathological features of papillary renal cell carcinoma (pRCC). Methods: A total of 128 pRCC in 115 patients who underwent preoperative MRI were characterised in terms of pathological type (type 1 vs. type 2), MRI appearance (focal vs. infiltrative) and additional MRI features. Patients were classified on the basis of the presence or absence of metastatic disease. Results: There were 65 focal type 1, 54 focal type 2 and 9 infiltrative pRCC. All infiltrative pRCC were of histopathological type 2. Renal vein thrombus was present in 89 % of infiltrative pRCC and no cases of focal pRCC. Metastatic disease was observed in 3.7 % of focal type 1, 7.5 % of focal type 2 and 75.0 % of infiltrative type 2 pRCC. Infiltrative MRI appearance was a significant predictor of metastatic disease, independent of pathological type, size and T stage (P ≤ 0.020). Among focal pRCC on MRI, pathological type 2 was not a significant predictor of metastatic disease (P = 0.648). No combination of features achieved significantly greater accuracy for predicting metastatic disease than renal vein thrombus alone (P > 0.5). Conclusion: Infiltrative MRI appearance and renal vein thrombus identify a subset of pathological type 2 pRCC at a significantly increased risk of metastatic disease. Key Points: • Magnetic resonance imaging (MRI) offers new preoperative insights into renal cell carcinoma (RCC). • Certain MRI features are associated with metastatic papillary RCC. • Metastases seem more common given an infiltrative appearance and renal vein thrombus.