Imaging of Chromophobe Renal Cell Carcinoma with ^99mTc-Sestamibi SPECT/CT: Considerations Regarding Risk...

Area of Science:

• Nephrology
• Radiology
• Oncology

Background:

• Indeterminate renal masses are frequently detected incidentally via cross-sectional imaging.
• ^99mTc-sestamibi SPECT/CT is utilized to differentiate oncocytomas and oncocytic renal neoplasms from other renal tumors.
• A subset of chromophobe renal cell carcinomas (chRCC) can exhibit uptake on these scans, leading to potential misclassification as false-positives.

Purpose of the Study:

• To re-evaluate the diagnostic accuracy of ^99mTc-sestamibi SPECT/CT in indeterminate renal masses.
• To determine the actual false-positive rate of chRCC in renal sestamibi scans.
• To refine the utility of SPECT/CT for risk stratification of renal neoplasms.

Main Methods:

• Retrospective review of patients who underwent renal sestamibi SPECT/CT for solitary tumors originally classified as chRCC between 2014 and 2023.
• Histopathological re-review of all cases using WHO 2022 criteria, with confirmatory immunohistochemistry for suspicious cases.
• Analysis of SPECT/CT findings in relation to the revised histopathological diagnoses.

Main Results:

• Out of 18 patients, 13 (72.2%) remained classified as chRCC, including 4 (22.2%) eosinophilic-variant chRCC.
• Five tumors (27.8%) were reclassified: 2 as low-grade oncocytic tumor (LOT), 1 as eosinophilic vacuolated tumor (EVT), and 2 as unclassified low-grade oncocytic neoplasms.
• Among qualitatively "hot" tumors, only 22.2% were non-eosinophilic chRCC; among "cold" tumors, only 11.1% were not chRCC.

Conclusions:

• The current histopathologic classification suggests that the "false-positive" rate of renal sestamibi uptake in chRCC might be overestimated.
• Further research is needed to optimize the use of renal sestamibi scans for non-invasive risk stratification of indeterminate renal masses.
• Accurate differentiation of renal tumor subtypes is crucial for appropriate patient management.