RENAL ONCOCYTOMA - MAGNETIC-RESONANCE-IMAGING CHARACTERISTICS

Purpose: We investigated the magnetic resonance imaging (MRI) appearan ce of renal oncocytomas. Materials and Methods: Between 1985 and 1993, 11 patients at our institution underwent MRI of the kidneys and were subsequently diagnosed with renal oncocytoma. Patient charts and MRI w ere reviewed. Results: Of 11 T1-weighted images 8 showed a mass with d ecreased signal intensity compared to renal cortex and 3 of 6 T2-weigh ted images revealed masses with increased intensity. In addition, 5 tu mors were surrounded by a well defined capsule, 3 demonstrated a centr al stellate architecture and 1 contained an area of central decreased signal, all of which corresponded pathologically to scar. These MRI fi ndings differ somewhat from those of renal cell carcinoma, which typic ally show intermediate to high signal intensity compared to renal cort ex on T1 and T2-weighted pulse sequences and usually contain evidence of either hemorrhage or necrosis. Conclusions: A low intensity homogen eous mass on T1-weighted images, which appears as increased intensity on T2-weighted images, the presence of a capsule, central scar or stel late pattern and the absence of either hemorrhage or necrosis suggest oncocytoma. It is in the evaluation of patients with a solitary kidney , poor renal function, advanced age or a small easily resectable renal mass when MRI may help diagnose an oncocytoma and, thus, allow renal sparing surgery. The optimal MRI to evaluate renal masses should inclu de T1-weighted spin echo images with and without gadolinium, T2-weight ed images and gradient recalled echo images.