Renal oncocytoma mimicking chromophobe renal cell carcinoma: Management using proposed diagnostic algorithm with emphasis on 99mTc-sestamibi SPECT/CT.

Renal oncocytomas are benign renal tumours characterized by a central stellate scar that are indistinguishable on CT/MR imaging from malignant chromophobe renal cell carcinomas (ChrRCCs). Renal oncocytomas and ChrRCCs can be separate entities but can also co-exist on a spectrum in hybrid oncocytic/ chromophobe tumours. In the past, invasive biopsy and pathologic diagnosis has been relied on to differentiate these lesion and direct management. Early research demonstrates the effectiveness of technetium 99m sestamibi (99mTc-sestamibi) single-photon emission computed tomography (SPECT)/CT in differentiating benign versus malignant renal tumours. A new diagnostic algorithm has previously been proposed to reduce unnecessary biopsy and/or targeted therapy in managing enhancing 1-4 cm renal masses by incorporating 99mTc-sestamibi SPECT/CT in management. We present a case of suspected renal oncocytoma found incidentally on surveillance imaging post-treatment of uveal melanoma. We illustrate the incorporation of the proposed diagnostic algorithm using 99mTc-sestamibi SPECT/CT for enhancing 1-4 cm renal masses into the existing diagnostic algorithm for incidental renal masses and demonstrate its use in our case of suspected renal oncocytoma.