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Introduction:A non-diagnostic (ND) renal mass biopsy (RMB) presents a clinical dilemma for the clinician and patient. We report the outcomes of our patients with non-diagnostic RMBs.
Materials & Methods:We retrospectively reviewed our single-institutional database of 1233 RMBs performed between 1998-2012 to identify non-diagnostic RMBs. ND pathology was defined as a report of (1)renal / non-renal tissue not representative of the lesion, (2)insufficient specimen. Rebiopsy, ablation, and surgery were defined as immediate if within 6 months of initial biopsy and without interval growth on CT. Subsequent outcomes after ND RMB were analyzed.
Results:Among 1233 RMBs performed, 266(22%) were ND. Of these, 129 were solid and 137 were cystic. Mean lesion size was 2.94 cm(SD=2.25). Of 266 ND biopsies, 91(34%) underwent immediate intervention (rebiopsy, surgery, or ablation), 148(56%) were placed under surveillance, and 27(10%) were lost to follow-up. Among those on surveillance 19(13%) ultimately underwent intervention, 1290(87%) remained stable over median follow-up of 3.2 years(IQR 1.1-4.3) . Mean tumor size in the immediate intervention group was 3.50 cm(SD=2.6) versus 2.59 cm(SD=1.7) in the surveillance group(p=0.0038). Of those undergoing immediate intervention 57.1%(52/91) of lesions were solid compared to 44.6%(66/148) on surveillance(p=0.0596). Ultimately, conclusive histopathology was available for 61 ND cases(36 rebiopsy, 25 surgery): 50(82%) were malignant(47 renal cell carcinoma, 2 transitional cell carcinoma, 1 metastases), 11(18%) were benign neoplasms.
Conclusions:A non-diagnostic RMB does not imply absence of malignancy. Immediate intervention or close surveillance imaging must be performed to establish tissue diagnosis or clinical behavior of lesions in patients with a non-diagnostic biopsy.