Perfusion of renal masses on MR corresponds to histopathologic diagnosis

By Liam Davenport, medwireNews Reporter

A magnetic resonance (MR) imaging technique that uses blood as a contrast medium is able to distinguish between different histopathologic diagnoses of solid renal masses based on their perfusion level, claims a team of scientists.

"Because ASL [arterial spin-labeling] perfusion values of oncocytoma and RCC [renal cell carcinoma] as well as papillary RCC and nonpapillary RCC subtypes seem to differ significantly, ASL MR imaging might contribute substantially to the noninvasive assessment of renal tumors and offer complementary results to those of percutaneous biopsy, particularly in those patients with inconclusive results," suggest Ivan Pedrosa, from UT Southwestern Medical Center in Dallas, Texas, USA, and colleagues.

The researchers performed ASL MR, which uses endogenous blood as a contrast medium by non-invasively labeling inflowing spins with radiofrequency and gradient fields of the MR unit, in 42 patients suspected of having renal masses before they underwent routine 1.5-T clinical MR examination.

Histopathologic findings, as the standard of reference, were available for 34 patients and correlated with perfusion values. In all, 28 patients had RCC, with clear cell RCC the most common subtype, followed by papillary, chromophobe, and unclassified RCC, affecting 15, five, four, and four patients, respectively.

The results, published in Radiology, show that there were significant differences for both mean tumor perfusion and peak tumor perfusion between histopathologic subtypes.

Specifically, the mean perfusion of oncocytoma (373.9 mL/min per 100 g) was significantly higher than that of papillary RCC (27.0 mL/min per 100 g), clear cell RCC (171.6 mL/min per 100 g), chromophobe RCC (152.9 mL/min per 100 g), and unclassified RCC (208.0 mL/min per 100 g). The mean perfusion of papillary RCC was also significantly lower than that of clear cell RCC, chromophobe RCC, unclassified RCC, and oncocytoma.

Furthermore, the mean peak perfusion of oncocytoma was significantly higher than that of papillary RCC, chromophobe RCC, and unclassified RCC, while the mean peak perfusion of papillary RCC was significantly lower than that of clear cell RCC.

There were no significant differences in mean and peak perfusion when tumors were divided by grade or stage, the team notes. Although there was a significant correlation between peak perfusion and clear cell RCC, there was no link between tumor size and mean perfusion.

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