Purpose: We investigated the magnetic resonance imaging (MRI) appearance 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 were reviewed.
Results: Of 11 T1-weighted images 8 showed a mass with decreased signal intensity compared to renal cortex and 3 of 6 T2-weighted images revealed masses with increased intensity. In addition, 5 tumors were surrounded by a well defined capsule, 3 demonstrated a central stellate architecture and 1 contained an area of central decreased signal, all of which corresponded pathologically to scar. These MRI findings differ somewhat from those of renal cell carcinoma, which typically show intermediate to high signal intensity compared to renal cortex on T1 and T2-weighted pulse sequences and usually contain evidence of either hemorrhage or necrosis.
Conclusions: A low intensity homogeneous mass on T1-weighted images, which appears as increased intensity on T2-weighted images, the presence of a capsule, central scar or stellate 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 include T1-weighted spin echo images and without gadolinium, T2-weighted images and gradient recalled echo images.