Preoperative Tumor Shape Irregularity Is Associated With Pathological Upstaging to pT3 in Clinical T1 Renal Cell Carcinoma Treated With Partial or Radical Nephrectomy

OBJECTIVES: We evaluate whether preoperative tumor shape irregularity (TSI) is associated with pathological upstaging to pT3 in clinical T1 renal cell carcinoma (RCC) after partial nephrectomy or radical nephrectomy. METHODS: We retrospectively reviewed 435 patients with clinical T1 RCC that underwent partial nephrectomy or radical nephrectomy between April 2007 and December 2025. TSI was graded as 1, 2, or 3 on preoperative computed tomography by three urologists. Inter-observer agreement was assessed using the complete agreement rate and overall kappa coefficient. Logistic regression analyses were performed to identify independent preoperative predictors of upstaging to pT3. RESULTS: Complete agreement for TSI was observed in 315 cases (72.4%), and the overall kappa coefficient was 0.64. Upstaging to pT3 occurred in 44 patients (10.1%), including one patient with pT3b. The rate of upstaging significantly increased across TSI categories, from 2.3% in TSI 1 to 15.7% in TSI 2, and to 63.6% in TSI 3 (p < 0.01). In multivariable analysis, higher TSI remained independently associated with upstaging, with ORs of 5.16 for TSI 2 and 32.30 for TSI 3 compared with TSI 1 (both p < 0.01). Clinical T1b stage was also an independent predictor (OR 4.93, p < 0.01). CONCLUSIONS: Preoperative TSI was independently associated with pathological upstaging to pT3 in clinical T1 RCC and may aid preoperative risk assessment when considering nephron-sparing surgery.