Characteristics of peritumoral pseudocapsule in small renal cell carcinoma and its influencing factors

BACKGROUND: The aim of this study was to investigate the peritumoral pseudocapsule (PC) status and identify the factors influencing PC status in small renal cell carcinoma (RCCs). METHODS: A total of 147 patients with small RCC (≤4 cm) who had undergone tumor enucleation (TE) were assigned into three groups according to PC status: complete PC, PC absence, and PC invasion. Computed tomography (CT) imaging and clinicopathological features were compared among the three groups. Univariate and multivariate analyses were performed to identify factors associated with incomplete PC. RESULTS: The number of patients with complete PC, PC absence, and PC invasion was 87 (59%), 20 (14%), and 40 (27%), respectively. Compared with the other two groups, tumors with complete PC were most common in clear cell RCC (CCRCC) and showed a hyperenhancement pattern (92%) and clear boundary (63%) on CT scanning images (p < 0.001). PC absence was most common in female patients (50%), whereas PC invasion was more common in male patients (85%) (p = 0.017). The tumor diameter in the PC absence group (2.24 ± 0.93 cm) was shorter compared with that of the complete PC group (2.88 ± 0.76 cm) and PC invasion group (3.16 ± 0.64 cm) (p < 0.001). Univariate and multivariate analysis showed that hypoenhancement pattern, unclear boundary, and non‐CCRCC subtype were independent risk factors of incomplete PC. CONCLUSIONS: Hypoenhancement pattern, unclear boundary, and non‐CCRCC subtype were significant predictors of incomplete PC in small RCCs. It remains to be established whether TE is an appropriate procedure for patients with incomplete PC.