EVIDENCE BASED UROLOGY
|Year : 2006 | Volume
| Issue : 1 | Page : 61-63
Role of needle biopsy in solid renal masses: When does the pudding require a proof?
J Chandra Singh, Nitin S Kekre
Department of Urology, Christian Medical College, India
J Chandra Singh
Department of Urology, Christian Medical College, Vellore
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Singh J C, Kekre NS. Role of needle biopsy in solid renal masses: When does the pudding require a proof?. Indian J Urol 2006;22:61-3
Fine-needle aspiration biopsy (FNAB) has been an accepted diagnostic modality for solid intra-abdominal masses in general. Whenever a solid renal lesion is identified on an imaging study, it has been observed that an advice for FNAB is given and it is promptly carried out in certain centers with an intention of proving the diagnosis. Though FNAB often confirms the diagnosis of renal cell carcinoma (RCC), the role of FNAB in the evaluation of solid renal masses is limited unlike in other abdominal masses. An insight into the role of this diagnostic test in clinical decision making will enable appropriate utilization of this investigation.
Imaging in solid renal masses
Sonography is most often used to evaluate a suspicious renal mass to determine whether it is a simple benign renal cyst or a potential malignant neoplasm. Approximately 42% of RCCs are isoechoic. Such tumors are usually recognizable, especially if they are over 3 cm in size or they distort the renal outline or central renal sinus echo complex. Even smaller lesions are detected on contrast enhanced CT scans. Features like contrast enhancement, calcification and alteration in morphology suggest a higher likelihood of malignancy and appropriate management decision should be made. On CT, solid renal masses may be hypodense, isodense or hyperdense as compared with renal parenchyma on non-enhanced CT scans. Occasionally, RCCs are markedly hyperdense on non-enhanced CT scans. Lesions may appear heterogenous on non-enhanced scans owing to hemorrhage and necrosis. Tumor calcification occurs in about 30% of cases of RCC, as detected by non-enhanced CT scans. After intravenous contrast medium, administration, most solid RCCs show enhancement. Enhancement is often heterogenous because of tumor hemorrhage and necrosis. The mass usually shows a rounded, lobulated margin and there is distinct demarcation from adjacent renal parenchyma.
Needle biopsy before surgical excision
RCCs comprise more than 90% of renal masses that are radiologically demonstrated to be solid. Unlike diagnostic dilemmas in other viscerae with a lesser pretest probability where a biopsy confirmation substantially increases the diagnostic accuracy, the contribution of FNAB is not significant in renal masses when an operative approach with curative intent is being planned. Hence if the patient is a candidate for curative resection in the form of radical or partial nephrectomy, there is little to be gained by FNAB. Furthermore, FNAB is associated with sampling error and non-diagnostic biopsies. Dehcet et al prospectively studied the sensitivity and accuracy of FNAB in patients undergoing radical or partial nephrectomy on 100 consecutive specimens removed during partial or radical nephrectomy. Tru-cut biopsy of the excised specimens was performed. Histopathology of the needle biopsy was compared with the pathologic features of the permanent section. Overall accuracy was 77% and 72% and the sensitivity was 81% and 83% respectively in radical and partial nephrectomies respectively. Hence based on a negative biopsy it cannot be assumed that the mass is innocuous. Depending on the other factors, either a radical or a partial nephrectomy is warranted. The high diagnostic yield of needle biopsy is negated by the fact that in those with a negative biopsy, absence of a neoplasm can be confirmed with reasonable certainty only by surgical removal of the lesion. False negative rates upto 15-25% has been reported. As 90% of solid enhancing lesions are RCCs it is pointless for them to be biopsied for even if it negative one would still go ahead and excise the lesion. Hence a needle biopsy has not significantly altered the clinical decision making in this scenario. Needle tract seedling, though infrequent, has been reported. Other complications include bleeding, pneumothorax and injury to other intra-abdominal viscerae have been reported. Hence fine-needle aspiration biopsy is contraindicated in those patients with a typical RCC and without a history of another primary malignancy. There is little to be gained by FNAB since surgical resection is the standard of care and patients would likely proceed to surgical resection regardless of the biopsy result due to the possibility of a false negative biopsy. FNAB is also not indicated in cases of suspected transitional cell carcinoma due to the high incidence of multiplicity and tumor seeding associated with this cell type since alternative means to establish the diagnosis are available.
Needle biopsy in indeterminate lesions
Indeterminate lesions on imaging were observed by Richter et al in 7.2% of 8140 renal mass lesions in a retrospective study. Most authors consider an enhancement of more than 20 HU significant. Hence lesions with enhancement between 10 HU and 19 HU characterize a mass as "indeterminate". Many series of FNAB report favorable role of FNAB, especially in those found to have a benign lesion on histopathology. Limitations in these series include lack of homogeneity in study population influencing diagnostic rates, poor diagnostic accuracy in malignancies, non-availability of corroborative excision biopsies for precise calculation of the negative predictive value, lack of convincing data on the adequacy of follow up in those diagnosed to have a benign lesion on biopsy, nondiagnostic biopsies ultimately relying on radiological findings for excision. Hence though a benign histopathology on FNAB in those with indeterminate lesions can avoid operative intervention, this should be resorted to only in those amenable for close follow up. Though Neuzillet et al have reported that a benign biopsy can avoid an operation in indeterminate masses, they have emphasized the importance of rigorous the follow up, as they have noticed a chromophobe RCC in a patient on follow up with a rapid increase in the size of the lesion.
Needle biopsy in metastatic and inflammatory lesions
In patients with disseminated metastatic disease, unresectable renal tumors or other contraindications to surgical intervention, needle biopsy enables establishment of a firm diagnosis, thus avoiding a surgical procedure. Presence of primary extra-renal lymphoma and an associated renal lesion suggests that a solitary renal or perirenal mass may be lymphoma. FNAB has enabled confirmation of metastatic lesions, avoiding unnecessary operative intervention to confirm diagnosis in these cases. Follow up of non-diagnostic biopsies in this group is hampered by death due to progression of non-renal tumor in the surveillance group. When there is a strong history of urinary tract infection or pyelonephritis suggesting that a renal lesion may be focal bacterial nephritis, exploration has been avoided following a negative biopsy.
Minimally invasive therapy and role of needle biopsy
When minimally invasive ablative techniques like radio frequency ablation and cryotherapy are considered for RCC, FNAB is useful to confirm the diagnosis prior to therapy. A positive biopsy enables institution of appropriate minimally invasive therapy, avoiding operative approach. Unfortunately, in cases of negative or non-diagnostic biopsies, the dilemmas are similar to those encountered in indeterminate masses.
| Conclusion|| |
Factors influencing the benefit of needle biopsy of solid renal lesions include technical success in obtaining specimen, reliable pathologic reporting of needle biopsy, avoidance of procedure related complications, possibility of avoiding an operative intervention based on a positive biopsy and rigorous follow up of patients who are managed non-operatively. FNAB is not indicated in a solitary renal lesion without a history of another primary malignancy and which is radiographically appears typical of RCC, when surgical excision is the treatment plan. This constitutes the commonest situation encountered in practice. FNAB is useful in metastatic RCCs to confirm the diagnosis and in those with a history of lymphoma or non-renal malignancies when metastases to the kidney are suspected. When minimally invasive techniques are considered, a positive FNAB provides tissue diagnosis prior to management, thus avoiding an operation. In those with indeterminate masses detected on imaging, the diagnostic yield is good but in those with a benign report, non-operative management can be recommended only if rigorous radiologic follow up can be ensured. Thus there are only a few definite indications where the pudding requires a proof.
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