Cystic Renal Masses Often Harbor High-Grade Disease

Almost a fourth of renal cysts had pathologically high-grade disease, which did not have a correlation with growth rate or increase the risk with active surveillance (AS), according to a large retrospective review.

Overall, 23% of 387 radiographically confirmed cystic lesions exhibited high-grade pathology. Nonetheless, the potentially more aggressive subset did not affect overall survival, which was similar between patients who had immediate surgery and those who opted for AS.

The findings challenge historical assumptions about the nature of the biologically heterogeneous cystic lesions, reported Randall A. Lee, MD, of Fox Chase Cancer Center in Philadelphia, and colleagues in the Journal of Urology.

In an email to MedPage Today, senior author Alex Kutikov, MD, also of Fox Chase Cancer Center, noted that "these findings elucidate the understanding that while these masses are typically safe to monitor, there exists a subset that may conceal high-grade disease. Therefore, in patients with a considerable life expectancy, surveillance should be executed with diligence. Appropriate discretion must be applied when determining appropriate timing of intervention."

"These insights highlight the safety associated with surveillance when it's employed by experienced providers," he added. "Moreover, the findings draw attention to the substantial proportion of masses, which, though appearing cystic in imaging, are ultimately confirmed as solid or necrotic on final pathology. This research underlines the necessity for continued work with a critical emphasis on distinguishing the cystic mass 'sharks' from the 'minnows.'"

Despite a rising incidence of renal cancer, disease-specific mortality has remained unchanged. The "treatment disconnect" can be explained in part by unnecessary detection and treatment of indolent lesions, Lee and co-authors noted in their introduction. As a result, "appropriate calibration" of treatment intensity is needed for incidentally discovered renal masses.

In particular, cystic masses are candidates for appropriate de-escalation of care, they continued. Cystic renal cell carcinoma (cRCC) encompasses a spectrum of lesions containing benign and malignant histologies. Pathologically confirmed cRCC has a recurrence-free survival approaching 100%, and cystic masses have better outcomes with AS as compared with solid masses.

Distinguishing preoperatively between indolent and more aggressive cRCC remains challenging. To address the issue, investigators examined the Fox Chase database of around 4,300 kidney masses managed with AS or intervention from 2000 to 2020. They focused on the association between radiographic tumor characteristics and high-grade pathology.

The data query identified 387 radiographically confirmed cystic lesions in 367 patients. Of those, 240 were resected and seven were ablated. Pathology reports showed that 23% of the cystic masses had high-grade pathology. The reports explicitly identified cystic lesions as such in only 18% of all cases, including 7% of high-grade lesions.

Evaluation of 184 patients on AS showed that Bosniak IV lesions had faster growth rates as compared with Bosniak IIF and III lesions. However, growth rate was not associated with presence of high-grade pathology. Cancer-specific survival was similar for patients who had surgery or ablation (99%) versus those on AS (100%).

The findings revealed a disconnect between cystic designation on imaging and pathologic findings. Despite the relatively high rate of high-grade disease in resected cystic lesions, AS with or without delayed intervention appears safe and effective for most radiographically cystic renal masses.

"We didn't expect to have this many aggressive tumors in there," said Kutikov. "It recharges the conversation about how we should describe, catalogue, and manage these masses."

The findings do not suggest "carte blanche" approval to operate on lesions that might be malignant, but rather that more research is needed.

"It's a call to action to really understand these masses better," he said.

Current imaging methods cannot identify features that might predict lesion aggressiveness, but that could change in the near future.

"Especially with artificial intelligence entering the radiology arena, there's clearly an opportunity here to tease out some variables that may not be evident on human review that could allow us to better risk stratify these lesions," said Kutikov.

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