Histopathologic analysis of tumor bed and peritumoral pseudocapsule after in vitro tumor enucleation on radical nephrectomy specimen for clinical T1b renal cell carcinoma.

PURPOSE

This study was designed to assess the feasibility and histopathologic safety of tumor enucleation for renal cell carcinoma, through histopathologic analysis of the tumor bed and peritumoral pseudocapsule (PC) after in vitro tumor enucleation.

MATERIALS AND METHODS

We studied 176 radical nephrectomy specimens for clinical T1b renal cell carcinoma in our institution, from January 2013-February 2016. Immediately after the kidney was excised, the tumor of radical specimen was enucleated in vitro. The tumor bed parenchyma of 15mm beyond the PC was examined to investigate the possible presence of tumor invasion or satellite lesions. The PC invasion was also evaluated.

RESULTS

The average tumor size was 5.7±0.7cm. The histopathologic evaluation revealed that 68.2% of tumors were clear cell renal cell carcinoma (RCC). The pathological staging showed that 92.6% of tumors were pT1b, 2.8% were pT2, and 4.5% were pT3a. For clinical T1b RCC, tumor infiltration on tumor bed was detected in 6 cases (3.4%), and satellite lesion was detected in 3 (1.7%). In the group of grade 1 to 2, 4 (2.3%) were found with residual tumor, and 5 (2.8%) in the group of grade 3 to 4 (P = 0.133). Papillary RCC had the highest rate of residual tumors (8.8%). A statistically significant association of peritumoral PC invasion with tumor size and pathologic grade was observed. Median follow-up was 23 months (range: 6-43) with a recurrence rate of 6.3% (11 of 176) and a cancer-specific mortality rate of 2.8% (5 of 176).

CONCLUSIONS

For clinical T1b renal cell carcinoma, the risks of tumor infiltration or satellite lesions on enucleation tumor bed or both are relatively low. Peritumoral PC invasion is associated with tumor size and pathologic stage. Tumor enucleation is a histopathologically safe technique for patients undergoing partial nephrectomy.