Tc-99m-Sestamibi SPECT/CT and histopathological features of oncocytic renal neoplasia

Background Tc-99m-Sestamibi Single Photon Emission Computed Tomography/Computed Tomography (SPECT/CT) contributes to the non-invasive differentiation of renal oncocytoma (RO) from renal cell carcinoma (RCC) by characterising renal tumours as Sestamibi positive or Sestamibi negative regarding their Tc-99m-Sestamibi uptake compared to the non-tumoral renal parenchyma. Purpose To determine whether Tc-99m- Sestamibi uptake in renal tumour and the non-tumoral renal parenchyma measured using Standard Uptake Value (SUV) SPECT, has a beneficial role in differentiating RO from RCC. Material and Methods Fifty-seven renal tumours from 52 patients were evaluated. In addition to visual evaluation of Tc-99m-Sestamibi uptake, SUVmax measurements were performed in the renal tumour and the ipsilateral non-tumoral renal parenchyma. Analysis of the area under the receiver operating characteristic curve identified an optimal cut-off value for detecting RO, based on the relative ratio of Tc-99m- Sestamibi uptake. Results Semiquantitative evaluation of Tc-99m-Sestamibi uptake did not improve the performance of Tc-99m- Sestamibi SPECT/CT in detecting RO. Tc-99m- Sestamibi SPECT/CT identifies a group of mostly indolent Sestamibi-positive tumours with low malignant potential containing RO, Low-Grade Oncocytic Tumours, Hybrid Oncocytic Tumours, and a subset of chromophobe RCCs. Conclusion The imaging limitations for accurate differentiation of Sestamibi-positive renal tumours mirror the recognised diagnostic complexities of the histopathologic evaluation of oncocytic neoplasia. Patients with Sestamibi-positive renal tumours could be better suited for biopsy and follow-up, according to the current active surveillance protocols.