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Page 2 of 5 Muttin et al. Mini-invasive Surg 2019;3:10 I http://dx.doi.org/10.20517/2574-

Renal tumor biopsy
In the context of SRM, RTB has been used to identify low- and high-risk malignant renal tumors, to reveal
a suspected metastasis in a non-renal neoplasm, to exclude lymphoma or abscess or, when an ablative
therapy (e.g., radiofrequency ablation) is planned, to obtain the histology or to confirm the success of
[4]
the treatment . Contraindications include comorbid and frail patients only suitable for conservative
management irrespective of biopsy results; patients with coagulation impairment; patients with a contrast-
[1,4]
enhanced renal mass for whom surgery is already planned .

According to a patient’s habits, anatomical tumor location and personal experience, ultrasounds and
computed tomography are conventionally used for guidance when RTBs are performed. Tissue sampling
[1,4]
can be realized with fine needle aspiration (FNA) and/or core biopsy (CB) . In FNA, a twenty-one-gauge
needle is inserted through a coaxial sheath to obtain multiple cytologic samples while limiting discomfort
and the risk of tumor seeding. For CB, an eighteen-gauge needle with the same coaxial technique provides
better diagnostic samples when at least 10 mm long cores are taken from the central and peripheral zones
while avoiding necrotic areas.

In a recent systematic review and meta-analysis, CBs have been found to have a better diagnostic accuracy
for the detection of malignancy compared to FNA, with a sensitivity of 99.1% vs. 93.2% and a specificity of
[3]
99.7% vs. 89.8%, respectively . Higher diagnostic accuracy is reached when large solid exophytic lesions
[1,2]
are biopsied or when a combination of the two techniques is performed . A non-diagnostic result can
occur in up to 8%-14.7% of all RTB (range 0%-22.6% for CB and 0%-36% for FNA). However, a repeated
biopsy is diagnostic in > 90% of cases. After surgical resection, the positive and negative predictive values of
RTB are > 99% and 70%, respectively [2,3,5,6] . When focusing on SRM only, RTB shows a sensitivity of 99.7%
and a specificity of 98.2%. Furthermore, after surgical resection of SRM only, the concordance rate for
tumor histotype is 96% while the concordance rate for tumor grade is 66.7% and increases to 86.5% when a
[3]
simplified low-high grading system is used .

Overall, RTB is feasible and safe when the coaxial technique is used. Morbidity after percutaneous sampling
is low (8.1%) and complications include spontaneous resolving subcapsular/perinephric hematoma (4.3%-
4.9%), clinically significant pain (1.2%-3%), self-limiting hematuria (1%-3.15%), pneumothorax (0.6%),
hemorrhage requiring blood transfusions (0.4%-0.7%) and infections. Fewer than 1% of the patients
experience major complications such as a gross hematuria or a pseudoaneurysm that requires embolization.
[3,5]
Anecdotal cases are reported for tumor seeding along the needle tract .

Active surveillance
Active surveillance (AS) is defined as the initial monitoring of tumor size by serial abdominal ultrasounds
or cross-sectional imaging with delayed treatment (DT) reserved for those patients whose SRMs show
[1]
clinical progression during the follow-up examination . Indications for AS are still controversial, thought
an elderly patient with a high surgical risk or competing risks of death and a very small low-growing renal
mass represents the optimal candidate for AS [Table 1]. A recent systematic review of the oncological
outcomes of currently published AS data indicates this treatment modality is a safe initial management
strategy for SRM, especially for patients with very small tumors (< 2 cm) and elderly and/or sicker patients
(> 75 years), followed by DT only if required because of progression. Specifically, metastatic progression
and cancer-specific mortality (CSM) rates for cT1a tumors have been found to be low, accounting for 0-6%
and 1%, respectively. Conversely, the other-cause mortality (OCM) rate is 1%-45%, reflecting the advanced
[7]
age and prevalence of comorbidities in these AS patients AS .

The data supporting these findings are manifold. Up to 52% of all resected SRM are suitable for AS, with
[8]
23% of benign histology and 29% of favorable risk or intermediate risk < 2 cm tumors . Moreover, a
significant proportion of SRM which satisfy the criteria of AS are benign tumors or low-grade renal cell