Investigators have identified criteria that predict which renal mass biopsies are likely to be non-diagnostic, according to a recently published report. Excluding patients with these criteria from biopsy decreased the non-diagnostic rate from 14.7% to 8.7%.

These factors include renal masses with cystic features, radiologic enhancement less than 20 HU, small size (less than 4 cm), and a skin-to-tumor distance of 13 cm or greater.

For the study, investigators from the University of Wisconsin School of Medicine and Public Health in Madison reviewed the records and pre-biopsy imaging for 525 patients at their institution who had renal tumors 7 cm or less.

Following biopsy, 14.7% of patients overall and 17.4% of patients with renal masses 4 cm or smaller had non-diagnostic findings, according to results published in The Journal of Urology (2015;193:1899-1904). For those undergoing a repeat biopsy, the rate of non-diagnostic findings was similar at 20.8%. Radiologist or pathologist experience was ruled out as a contributing factor.

“In patients with tumors at a distance of 13 cm or greater from the body surface the rate of non-diagnostic biopsy was 27%, likely reflecting the increased technical difficulty of maneuvering the biopsy needle in deep tissue and the decreased visualization of the needle and tumor when using US guidance for these biopsies,” the authors wrote. 

Tiny tumors, cystic masses with small areas of malignant cells, and lack of radiological enhancement also present targeting challenges. 

1. Prince, J, et al. The Journal of Urology; doi: 10.1016/j.juro.2014.12.021.

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