RENAL BIOPSIES FOR EVALUATION OF SMALL RENAL MASSES: EXPERIENCE OF A SINGLE UROLOGICAL CENTER.

Objective

There has been an increase in the diagnosis of incidental small renal masses; an increasing number of renal lesions are difficult to classify into either benign or malignant categories on the basis of their imaging characteristics alone. The fear of leaving a potentially curable malignant tumour or overtreating a benign lesion poses a vexing management problem in these masses.
The use of percutaneous biopsy of renal tumours has been traditionally reserved for selected cases because of uncertainties regarding its safety, accuracy and clinical utility. With the adoption of modern biopsy tehniques and increasing expertise in interpreting biopsy specimens, renal tumour biopsy today has limited morbidity and allows histologic diagnosis in the majority of cases in centres with expertise. Aim of this study is to critically appraise and determine the impact of image-guided biopsy on the management of small renal masses

Methods and results

Data were collected for all the consecutive patients requiring renal core biopsies for the diagnosis of indeterminate renal masses between June 2009 and February 2014.
All biopsies were perfomed for histologic confirmation in planning management, surveillance or active intervention (surgery or micro wave ablation) or, in the post ablation period, for suspicion of recurrence.
Biopsy procedure: the renal core biopsies were taken under ultrasound guidance, using local anaesthetic. A 17-gauge guiding cannula and a 18-gauge core needle was used in multiple passes through different areas of each mass, and the core specimens obtained were placed in 10% formalin solution and sent for pathologic analysis.After the procedure, patients were observed for a minum of 24 h, during which their pulse and blood pressure were monitored and the biopsy site was observed for any swelling or haematoma.
35 patients, median age 77 (50-86), underwent 48 renal biopsies for renal masses. Median size of renal masses was 3,2 cm (2-6 cm), median number of biopsy core was 3 (2-4).
Of the 48 biopsies 24 were diagnosed as renal malignancies: 19 conventional RCCs (1 after micro wave ablation), 1 papillary RCCs, 3 chromophobe RCCs, 1 transitional cell carcinoma; 10 benign lesions included: 2 oncocytomas, 3 angiomyolipomas and 5 complex cysts; 1 patients had nonrenal malignancy diagnosed (non-Hodgkin's lymphoma). 8 biopsies were negative control after thermal ablation of renal tumous; 5 patients had nondiagnostic biopsies.
All patients were discharged on the first day after biopsy, except one who had persistent hematuria that required embolisation. Needle tract seeding was not seen in our series.
Among the patients with renal malignancies,16 underwent thermal ablation with micro wave, 4 radical nephrectomy, 4 partial nephrectomy and 1 embolisation.
When available, the final histopatology was similar to the findings of the biopsy specimen.

Discussion

Renal tumour biopsies had historically selective indications. With the use of modern techniques, percutaneous biopsies can be performed with low morbidity, no risk of seeding and good diagnostic yield and accuracy for malignancy and histotype in centres with expertise.
In recent years, the increasing incidence in the diagnosis of incidental small renal masses, the developement of conservative and minimally invasive treatments for low-risk RCC, and the novel target therapy for metastatic disease have provided the rationale for expanding indications of renal tumour biopsies.
At present, percutaneous biopsy is recommended in the diagnostic work-up of renal tumours that are indeterminate on imaging and of incidentally detected small renal masses in patients at high surgical risk to support treatment decisions and avoid unnecessary surgery.
When indicated, biopsies shoul be also increasingly performed after thermal ablation of renal tumours.
Despite the increasing experience and indications, biopsies are still significantly underutilised. Further clinical research is needed to overcome the current limitations of renal tumour biopsies and increase their application in clinical practice.

References

Image-guided biopsy-diagnosed renal cell carcinoma: critical appraisal of technique and long-term follow-up. Somani BK, Nabi G, Thorpe P, N'Dow J, Swami S, McClinton S; Aberdeen Academic and Clinical Urological Surgeons (ABACUS) Group. Eur Urol. 2007 May;51(5):1289-95