Glycosaminoglycans (GAGs) were significantly altered in localized as well advanced RCC compared to healthy samples. In addition, GAG scores correlated with progression-free survival and overall survival (OS) in a prospective cohort of patients with metastatic ccRCC and localized RCC. However, it is still unknown whether alterations in plasma and urine GAGs are exquisitely specific to RCC or are shared by other benign lesions in the kidney, such as angiomyolipomas, oncocytomas, or PEComa.