Fig. 3.

MR images of a 79-year-old man with a renal mass. Axial single-shot T2-weighted image (a) shows a large T2-hypointense poorly encapsulated infiltrative mass involving nearly the entire right renal parenchyma (solid arrow), consistent with MRI appearance III. There is also tumour thrombus throughout the right renal vein and extending into the inferior vena cava (IVC) (dashed arrows). Although the mass was diagnosed as a type 2 papillary renal cell carcinoma (pRCC) at total nephrectomy, the mass was classified as infiltrative pRCC in our study. Section of tumour (b) shows a central area with small neoplastic nuclei without prominent nucleoli, indicative of low nuclear grade, in comparison with focal areas at the periphery with larger nuclei and associated eosinophilic cytoplasm, indicative of high nuclear grade (H&E stain, x400); overall, the lesion was classified as predominantly low nuclear grade, with high nuclear grade areas present. Chest CT performed at the time of initial presentation (not shown) demonstrated a massive pulmonary embolus. In addition, nodal micrometastases were identified at the time of nephrectomy, although these were not evident on preoperative imaging