International Urology and Nephrology (2018) 50:1205–1209
UROLOGY - ORIGINAL PAPER
Core needle biopsy clarify the histology of the small renal masses
and may prevent overtreatment
N. H. Azawi
· S. A. Tolouee
· M. Madsen
· K. D. Berg
· C. Dahl
· M. Fode
Received: 1 March 2018 / Accepted: 30 April 2018 / Published online: 30 May 2018
© Springer Science+Business Media B.V., part of Springer Nature 2018
Purpose The purpose of the study was to evaluate the diagnostic accuracy of core biopsy in small renal masses ≤ 4 cm in
response to the rising prevalence of renal masses.
Methods Data from 129 consecutive patients who underwent biopsies of solid renal masses of ≤ 4 cm were prospectively
collected between September 2014 and January 2017. In cases with inconclusive biopsies, a repeat biopsy was recommended.
Histology from surgical specimens was used as gold standard to evaluate the accuracy of renal biopsies.
Results The initial biopsies revealed malignancy in 77 patients (59.7%) and benign histology in 35 patients (27.1%), whereas
17 (13.2%) were inconclusive. Fifty-six patients with malignant histology underwent either partial or radical nephrectomy
according to the physicians’ recommendation, while two patients with benign histology requested surgery. In all cases, the
biopsy diagnosis was conﬁrmed upon ﬁnal histopathology. Of the inconclusive cases, six underwent repeat biopsies all with
benign histology. Further, three patients opted for immediate partial nephrectomy with benign oncocytoma in two and renal
cell carcinoma in the third. The remaining eight patients opted for follow-up CT scans with no sign of progression with a
minimum of 6-month follow-up. No biopsy related complications were reported in the ﬁrst 30 days after RTB. Overall, the
treatment strategy changed in 45 of 129 (35%) patients due to biopsy results. This was either due to benign ﬁndings or due
to the discovery of non-renal cell cancers.
Conclusion Core needle biopsies of solid renal masses ≤ 4 cm have excellent accuracy and may be used to select the correct
treatment. Importantly, they may serve to prevent overtreatment of benign tumors.
Keywords Overtreatment of small renal masses · Small renal masses · Renal cell carcinoma · Ultrasound-guided biopsy
The incidence of incidentally detected small (≤ 4 cm)
asymptomatic renal tumors has increased dramatically due
to an increase in CT scans for other indications . This has
prompted an increase in surgery for kidney masses; however,
mortality from kidney cancer has not decreased, most likely
reﬂecting that a large proportion of these tumors are slow-
growing/indolent . Unfortunately, multiphase helical CT,
which is the standard imagining modality used to diagnose
renal masses, only has limited ability to distinguish between
tumor types . Likewise, magnetic resonance imaging
(MRI) has a tendency to upgrade complex cystic changes 
and although contrast-enhanced ultrasound has improved our
ability to diﬀerentiate tumors, it is inﬂuenced by bowel gas,
obesity or tumor location, and it requires suﬃcient experi-
ence . The impact of these limitations was recently dem-
onstrated in a surgical series from our department, where
benign histology was found in 20% of solid renal masses
of ≤ 4 cm following partial or radical nephrectomies .
Consequently, we now oﬀer routine core needle renal tumor
biopsies (RTB) in such cases to clarify the histology prior
Electronic supplementary material The online version of this
article (https ://doi.org/10.1007/s1125 5-018-1885-y) contains
supplementary material, which is available to authorized users.
* N. H. Azawi
Department of Urology, Zealand University Hospital,
Sygehusvej 10, 4000 Roskilde, Denmark
Institute of Clinical Medicine, University of Copenhagen,