Low biopsy volume in ureteroscopy does not affect tumor biopsy grading in upper tract urothelial carcinoma

Objectives: Urothelial carcinomas (UC) from the upper urinary tract represent 7%-10% of all kidney malignancies. With current ureteroscopic (URS) techniques, small tissue samples are usually the only available histopathologic material for evaluation, representing a diagnostic challenge. Precision in diagnosis is essential for treatment decision making. There has been much debate as to whether tumor grade and stage found on biopsy agree with final pathology. The purpose of this study is to evaluate whether URS biopsy volume affects tumor grading and staging agreement between biopsy and nephroureterectomy (NU) specimens.

Materials and methods: We reviewed 137 URS biopsies in 81 patients with suspected upper urinary tract UC performed from April 2002 to April 2011. Of those, 54 patients had both the URS biopsy and NU performed at our institution and were available for review. Biopsy dimensions were recorded to calculate estimated ellipsoid volume, and 2 urological pathologists independently evaluated histologic grade (ISUP/WHO 2004), (based on pleomorphism and mitosis) and depth of invasion. Statistical analysis was performed to evaluate URS biopsy and NU specimen grade and stage concordance. In addition, univariable and multivariable analyses was performed to assess the effect of biopsy volume on agreement.

Results: Of the 54 patients studied, low grade and high grade UC biopsy were found in 8 (15%) and 46 (85%), URS biopsies, respectively. Regarding biopsy stage, 51 (94%), 1 (2%), and 2 (4%) were stage Ta, T1, T2, respectively. Grade concordance was 92.6%, (95% CI: 82.4%-98.0%). Stage concordance was 43% (95% CI: 28.7%-55.9%). Multivariable analysis showed biopsy volume did not affect tumor assessment of grade (P = 0.81) or stage (P = 0.44).

Conclusions: Histologic grade assigned on the URS biopsy sample accurately predicts histologic grade in the resected specimen (92.6%), even when the biopsy volume is small. Grading in URS biopsies provides sufficient information for clinical decision making that is independent of sample volume.