[Emphasizing the pathological features and clinical significance of the pseudocapsule in renal cell carcinoma]

The pseudocapsule of renal cell carcinoma (RCC) is a fibromuscular interface structure formed by the compression of adjacent renal parenchyma during expansile tumor growth, which subsequently triggers fibrous connective tissue proliferation, inflammatory response, and tissue remodeling. In recent years, with advances in pathology, radiomics, and molecular biology, the pseudocapsule is no longer considered a mere passively formed fibrous encapsulation, but rather a dynamic tumor-host interface actively involving tumor cells, stromal cells, inflammatory cells, blood vessels, and the extracellular matrix. On the one hand, the pseudocapsule can restrict tumor extension through its dense fibrous architecture; on the other hand, aberrant vascular remodeling, matrix degradation, and alterations in the immune microenvironment within the pseudocapsule may contribute to local invasion, nutrient supply, and potential metastasis. Therefore, the integrity, thickness, continuity, and tumor breakthrough of the pseudocapsule may carry important prognostic value. This review summarizes the pathological features, formation mechanisms, imaging evaluation, and molecular basis of the pseudocapsule in RCC, as well as their associations with tumor progression and prognosis. Furthermore, based on current pathological reporting standards, actionable recommendations for pseudocapsule reporting in clinical practice were proposed, aiming to provide references for preoperative assessment, surgical strategy selection, and prognostic prediction in patients with RCC.