Small renal masses (diameter ≤4 cm) are being detected more and more frequently thanks to the widespread use of diagnostic imaging. However, distinguishing benign lesions from malignant ones remains a significant clinical challenge: up to 30% of surgically removed masses are found to be benign upon histological examination. This leads to potentially avoidable surgical procedures, with the associated risks for the patient.
Our researchers wanted to assess whether combining two imaging techniques—magnetic resonance imaging (MRI) and SPECT/CT scintigraphy with technetium-99m sestamibi—could improve the preoperative characterization of these lesions, particularly distinguishing clear cell renal cell carcinoma (ccRCC), the most common and aggressive form of kidney cancer.
Eighteen patients with indeterminate renal masses at clinical stage T1a were analyzed. Each lesion was assigned an MRI score called the "clear-cell likelihood score" (ccLS), a scale from 1 to 5 that estimates the probability that the mass is a ccRCC. At the same time, sestamibi scintigraphy was performed, which exploits the differences in mitochondrial content between different types of tumors: benign lesions such as oncocytomas show high uptake ("avid"), while carcinomas generally do not.
MRI alone correctly identified ccRCC in over 90% of cases with a ccLS score of 4-5 (high probability). However, for lesions with an intermediate score (ccLS 3), accuracy dropped to 72%. The addition of sestamibi scintigraphy in these doubtful cases allowed a diagnostic accuracy of 94% to be achieved.
The authors therefore propose a new diagnostic pathway: first perform MRI with ccLS calculation for all indeterminate renal masses, reserving sestamibi scintigraphy for cases with intermediate scores. This approach could be particularly beneficial in elderly patients or those with comorbidities, avoiding unnecessary invasive biopsies or surgery.
Although preliminary and limited by the small sample size, these results suggest that combining two widely available and safe methods may optimize the diagnosis of small renal masses, reducing the need for unnecessary invasive procedures.
Bertini A, Basile G, Prato F, Zurrida R, Imperiale G, Brembilla G, Bertini R, Rosiello G, Salonia A, Larcher A, Chiti A, Montorsi F, De Cobelli F, Capitanio U. MRI in combination with Technetium-99m-sestamibi single-photon emission CT/CT: a novel diagnostic algorithm to maximize the characterization of small renal masses. BJU Int. 2026 Feb;137(2):262-264. doi: 10.1111/bju.70002. Epub 2025 Sep 23. PMID: 40984822.
