BACKGROUND: Tumour pseudocapsule shows plasticity, whose representative indicator- pseudocapsule thickness- was little studied in clear cell renal cell carcinoma (ccRCC). METHODS: We enrolled 1037 ccRCC patients who underwent surgery between 2006 and 2013 at our institution. The patients did not receive therapy before surgery and were confirmed to have a pathological pseudocapsule. The associations of pseudocapsule thickness with overall survival and disease-free survival were studied using multivariable Cox regression analyses. Patients were stratified using points of maximum separation. Influential factors were examined with logistic regression. RESULTS: The average thickness was 0.47 mm (median: 0.43, interquartile range: 0.28-0.6). The average follow-up was 92.1. In multivariable analyses, every 0.1-mm increase in thickness resulted in a decreased risk of death (hazard ratio (HR) 0.906, p = 0.011) but not recurrence (HR 0.948, p = 0.105). For patients with a pseudocapsule thickness of 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm and 1.0 mm, the estimated 10-year overall survival rates were 74.9%, 83.3%, 87.8%, 90.1% and 91.0%, and the 10-year disease-free survival rates were 69.6%, 76.6%, 80.8%, 83.1% and 84.1%, respectively, with the best cut-off value being approximately 0.37 mm. The results of logistic regression revealed that female sex (p <
0.001), age (p = 0.002), a higher neutrophil count (p = 0.011), large tumour size (p <
0.001) and necrosis (p = 0.011) were independently associated with a thin pseudocapsule (≤ 0.37 mm). CONCLUSIONS: Pseudocapsule thickness is heterogeneous in clear cell renal cell carcinoma. Generally, increased thickness is associated with improvement in long-term survival. A pseudocapsule being 0.37 mm or thinner is mostly influenced by both systematic and tumor-related parameters.