Are there parameters that predict a nondiagnostic biopsy outcome taken during laparoscopic-assisted cryoablation of small renal tumors?

Background And Purpose: The histopathologic diagnosis of a small renal mass (SRM) that is managed with cryoablation relies on preoperative or intraoperative biopsies. Because a considerable number of these SRMs are benign, accurate diagnosis has prognostic and follow-up implications. The main problem in SRMs is the high rate of nondiagnostic biopsies. Our purpose was to assess whether certain tumor and biopsy characteristics are correlated with a diagnostic biopsy outcome.

Patients And Methods: One hundred tumors that were smaller than 4.5 cm in 94 patients were managed with laparoscopic cryoablation. After dissection of the perirenal fat and identification of the tumor by intra-abdominal ultrasonography, one or more biopsies were obtained before freezing. Using the Student t/Mann Whitney U test, the following parameters were evaluated for predicting biopsy outcome: Tumor size, location, and exophytic part of the tumor, size of the biopsy needle, the number of biopsies taken, and presence of nonenhancing areas compatible with necrosis inside the tumors. Correlations among parameters were assessed using a Spearman correlation or Kruskal-Wallis test.

Results: Twenty-two (22%) biopsies were nondiagnostic and consisted of normal kidney tissue, connective tissue, fat, fibrosis, necrosis, and/or blood. There were no significant differences in parameters between the diagnostic and nondiagnostic group. There was a positive correlation between tumor size and number of biopsies (P=0.029) and between the presence of nonenhancing areas and both size (P<0.001) and the number of biopsies taken (P<0.001).

Conclusion: No statistical significant correlation was found between biopsy outcome and tumor or biopsy characteristics. More biopsies were taken in larger tumors, and larger tumors contained more nonenhancing areas that were suspect for necrosis.