Most of the 60,000 Americans diagnosed yearly with renal cell carcinoma (RCC) have a type identified by pathologists as “clear-cell renal cell carcinoma,” based on its characteristic appearance under the microscope. There are less common types of RCC, such as papillary and chromophobe – and then there are a number of kidney tumors each year that don’t fit any of these categories, and thus are known as “unclassified RCC.”

“A better understanding of unclassified RCC is needed to improve treatment for patients with these rare types of tumors,” says pathologist Andres Matoso, M.D., who led a recent study to shed light on these tumors. “We evaluated 79 patients with unclassified RCC and were able to accurately categorize those tumors, based on newly available pathological analyses,” Matoso says. Although the team was not able to classify all the tumors, “we were able to identify groups of extremely aggressive cancers and those with a better prognosis. We hope these results will provide a pathway moving forward to clarify treatment.” This work was published in the American Journal of Surgical Pathology.