Differentiation of renal cell carcinoma subtypes by multislice computerized tomography

Purpose

We differentiated renal cell carcinoma subtypes using multislice computerized tomography (CT).

Materials and Methods

We reviewed the CT images of 87 patients with renal cell carcinoma. Three subtypes of renal cell carcinoma were noted, including clear cell in 37 cases, papillary in 26 and chromophobe in 24. Biphasic CT (unenhanced, corticomedullary and excretory phases) was done in all patients. We compared patient age and sex, tumor size, enhancement degree and pattern (homogeneous, heterogeneous and predominantly peripheral), the presence or absence of calcification or cystic degeneration (necrotic or hemorrhagic areas within the tumor) and tumor spreading patterns, including perinephric change, venous invasion and lymphadenopathy, in the 3 subtypes.

Results

The degree of enhancement was significantly different among the 3 subtypes in the corticomedullary and excretory phases (p <0.001). Cystic degeneration was more evident in the clear cell subtype than in the other subtypes regardless of tumor size (p <0.001). A hypervascular pattern (higher tumor enhancement after contrast material injection due to higher vascularity) was noted in 48.6% of clear cell subtype in comparison to 15.4% of papillary and 4.2% of chromophobe subtypes (p <0.001). The chromophobe subtype showed homogeneous enhancement in 75% of cases in comparison to 45% and 65% of clear cell and papillary subtypes (p >0.05). Calcification was evident in 21.6%, 23.1% and 25% of clear cell, papillary and chromophobe subtypes, respectively (p >0.05).

Conclusions

To differentiate the subtypes of renal cell carcinoma the degree of enhancement is the most valuable parameter. The presence or absence of cystic degeneration, vascularity and enhancement patterns can serve supplemental role in differentiating renal cell carcinoma subtypes.     

Computerized tomography guided percutaneous renal cryoablation with the patient under conscious sedation: initial clinical experience

PURPOSE: We report on our initial clinical experience with CT guided percutaneous renal cryoablation. MATERIALS AND METHODS: CT guided percutaneous renal cryoablation was performed on 27 tumors using conscious sedation in 20 patients. Eligible patients had tumors of 5 cm or less and were poor surgical candidates or otherwise warranted nephron sparing treatment. Tumors were classified as central or noncentral depending on their relationship to the renal sinus fat. During cryoablation intraoperative active ice ball formation was monitored with real-time CT imaging to ensure adequate tumor coverage. Postoperative followup imaging was obtained at regular intervals. RESULTS: Our method appears technically feasible as of the 27 cryoablations performed, only 1 complication occurred requiring blood transfusion in a patient with a large, centrally located tumor. To date we have 16 tumors in 12 patients with imaging followup of 1 month or more (mean followup 5.9 months). Mean baseline tumor size in this group was 2.5 cm with 11 small (3 cm or less) and 5 large (more than 3 cm) tumors. Of the tumors 5 were centrally located and 11 were noncentrally located. Preliminary data suggest that of the 16 cryoablated tumors 15 showed no signs of enhancement on followup. CONCLUSIONS: CT guided percutaneous renal cryoablation appears to be a feasible treatment option for small, noncentrally located renal tumors. While early results appear promising, longer followup is needed to more clearly define the role of this treatment method.     

Percutaneous computerized tomography guided renal cryoablation using local anesthesia: pain assessment

PURPOSE: The administration of intravenous sedation during prone computerized tomography guided, percutaneous procedures has the potential for complications. We assessed the pain associated with computerized tomography guided, percutaneous renal cryoablation using straight local anesthesia. MATERIALS AND METHODS: Patients were treated with cryoablation probes inserted into the renal tumor under computerized tomography guidance with local anesthesia. Patients were asked to rate the pain experienced during needle placement and cryoablation using a visual 10-degree pain score scale. Sedation was given when pain was greater than 7 or when requested by the patient. Parameters assessed were cardiopulmonary complications, the need for intravenous supplementation, the pain score during the procedure and the postoperative score. RESULTS: A total of 25 patients (30 tumors) underwent a total of 26 cryoablation sessions with only local anesthesia. Mean patient age +/- SD was 67 +/- 13 years (range 33 to 88). Average tumor and ice ball size was 2.1 +/- 0.7 (range 1.1 to 4.3) and 4.1 +/- 1.0 cm (range 2.6 to 5.9), respectively. The mean dose of 1% lidocaine was 43.89 +/- 24.97 ml (range 10 to 110). All procedures were completed in an average of 68.78 +/- 20.7 minutes (range 40 to 120). Vital signs were not significantly changed during the procedure. Successful completion of percutaneous computerized tomography guided cryoablation using local anesthesia was accomplished in 22 of the 26 sessions (84.62%) without sedation. Four patients required intravenous supplementation. CONCLUSIONS: Percutaneous computerized tomography guided cryoablation for renal tumors can be performed using local anesthesia with minimal discomfort in most patients.     

Percutaneous renal cryoablation of renal tumors in patients with von Hippel-Lindau disease

PURPOSE: We determine the feasibility and safety of performing percutaneous cryoablation of renal tumors in patients with von Hippel-Lindau disease. MATERIALS AND METHODS: We selected 2 men and 2 women with von Hippel-Lindau disease and radiographic determined solid renal tumors were selected to undergo percutaneous cryoablation. All patients underwent standard preoperative evaluation. An interventional magnetic resonance imaging unit was used for probe guidance and ice ball monitoring. The cryoablation procedure was performed with a 2 or 3 mm. cryoprobe using a pressurized argon gas system for ice ball formation. The patients were hospitalized overnight for observation and discharged home the following day. A followup computerized tomogram or magnetic resonance imaging scan was performed at 1 week, 1, 3, 6 and 12 months and every 6 months thereafter, along with physical examination, urinalysis, serum blood urea nitrogen and creatinine. RESULTS: A total of 5 tumors were treated ranging from 2.8 to 5.0 cm. in diameter. All patients underwent the procedure without difficulty with 2 requiring re-treatment due to residual tumor for a total of 7 treatments. At followup from 2 to 23 months there has been no radiographic evidence of recurrence at the cryoablated areas. CONCLUSIONS: Percutaneous cryoablation of renal tumors in patients with von Hippel-Lindau disease proved to be successful in this initial series. Although 2 patients had residual tumor after the initial cryoablation procedure re-treatment was performed with no adverse sequela. This minimally invasive therapy may allow patients with von Hippel-Lindau disease to avoid the necessity of multiple open surgical procedures.     

Guidelines for the surveillance of localized renal cell carcinoma based on the patterns of relapse after nephrectomy

PURPOSE: We characterized relapse patterns in patients with sporadic renal cell carcinoma (RCC) following radical and partial nephrectomy, and developed surveillance guidelines. MATERIALS AND METHODS: Between 1989 and 2000, 495 patients underwent nephrectomy for RCC at 1 of 5 Canadian referral centers. Median followup was 42 months. RESULTS: The rate of relapse, time to relapse and site of relapse were associated with pathological stage. Five-year progression-free probability was 93% for pT1, 81% for pT2, 67% for pT3A and 57% for pT3B (p <0.001). Compared to patients with pT1-2 those with pT3A-B lesions had earlier relapse after nephrectomy (median 12 vs 26 months, p = 0.001) and were at higher risk for relapse at abdominal sites (14% vs 1.8%, p < 0.001). Abdominal relapse was detected in the absence of symptoms, abnormal biochemical profile or thoracic metastases detectable by chest x-ray in 7 patients (1.4%) overall, including 3 (0.9%) with pT1, 3 (4%) with pT3A and 1 (3%) with pT3B. CONCLUSIONS: The risk and the pattern of relapse of RCC after nephrectomy are associated with pathological stage. For the surveillance of recurrent disease after nephrectomy we recommend annual clinical assessment and chest x-ray in pT1-2 cases. Patients with pT3A-B should be followed every 6 months for the first 3 years with clinical assessment and chest x-ray, and annual followup thereafter. The higher risk of abdominal relapse in patients with pT3A-B indicates that they should receive surveillance abdominal imaging. We recommend abdominal computerized tomography 6, 12, 24 and 36 months postoperatively.     

Percutaneous cryoablation of renal cell carcinoma guided by horizontal open magnetic resonance imaging

BACKGROUND: Cryoablation is a treatment option for some patients with small exophytic lesions of the kidney. The purpose of this study is to determine the feasibility, safety, and intermediate-term treatment outcome of percutaneous cryoablation of renal cell carcinoma guided by horizontal open magnetic resonance imaging (MRI). METHODS: We prospectively used cryoablation to treat 13 patients with radiographically confirmed enhancing small, solid renal tumors (< or =4.8 cm). An argon gas-based cryoablation system was used. One to four cryoprobes with 2 or 3-mm diameters were placed percutaneously into the tumor under local anaesthesia and MRI guidance. Ice ball dimensions were monitored by 2-D MR images. Double freeze-thaw cycles were conducted throughout the procedure. After successful cryoablation, patients were followed on a regular basis to evaluate the treatment's clinical outcome. RESULTS: Median follow up from time of procedure is 35 months (range, 28-42). In all cases the entire procedure was accomplished without significant morbidity or complications. A mild retroperitoneal hematoma, which subsided spontaneously, was noted in one patient. Follow-up dynamic computed tomography (CT) at 3 months after operation confirmed the absence of enhancement in resolved tumor masses for 11 of 13 cases. None of these 11 patients had clinical evidence of recurrent disease at last follow up. The remaining two patients had lesions with some enhanced areas. Subsequent partial nephrectomy histologically confirmed the presence of vital tumor in, respectively, the center and the periphery of the residual masses. One of these patients developed multiple lung and ipsilateral adrenal metastases 13 months after surgical resection. CONCLUSIONS: Percutaneous cryoablation of small renal cell carcinomas under horizontal open MRI guidance appears to be safe and feasible. An intermediate-term follow up continues to demonstrate efficacy in most patients; however, a few patients experience incomplete ablation with risk of treatment failure. The ideal candidates for this procedure still need to be determined in longer follow up with diligent observation.     

Clinical use of fluorodeoxyglucose F 18 positron emission tomography for detection of renal cell carcinoma

PURPOSE: We evaluate the role of fluorodeoxyglucose F 18 positron emission tomography (PET) in patients with renal cell carcinoma (RCC) by retrospective review. To our knowledge this series is the largest reviewing the use of PET in patients with RCC. MATERIALS AND METHODS: A total of 66 patients who underwent 90 PET scans for suspected or known RCC were identified. Dictated reports of PET, chest computerized tomography (CT), abdominal/pelvic CT and bone scan were examined with confirmation of results by histopathology or followup of at least 1 year. The accuracies of PET and conventional imaging modalities were compared. RESULTS: PET exhibited a sensitivity of 60% and specificity of 100% for primary RCC tumors (abdominal CT demonstrated 91.7% sensitivity and 100% specificity). For retroperitoneal lymph node metastases and/or renal bed recurrence, PET was 75.0% sensitive and 100.0% specific (92.6% sensitivity and 98.1% specificity for abdominal CT). PET had a sensitivity of 75.0% and a specificity of 97.1% for metastases to the lung parenchyma compared to 91.1% and 73.1%, respectively, for chest CT. PET had a sensitivity of 77.3% and specificity of 100.0% for bone metastases, compared to 93.8% and 87.2% for combined CT and bone scan. In 39 scans (32 patients) PET failed to detect RCC lesions identified by conventional imaging. CONCLUSIONS: The role of fluorodeoxyglucose F 18 PET in the detection of RCC is limited by low sensitivity. With superior specificity PET may have a complementary role as a problem solving tool in cases that are equivocal on conventional imaging.     

Accuracy and clinical role of fine needle percutaneous biopsy with computerized tomography guidance of small (less than 4.0 cm) renal masses

PURPOSE: We evaluated the accuracy and clinical role of fine needle percutaneous biopsy of solid renal masses 4.0 cm or smaller with helical computerized tomography (CT) guidance. MATERIALS AND METHODS: In 88 consecutive patients (mean age 61 years) 88 biopsies were performed. Median tumor size was 2.8 cm. Tumor biopsy was performed with an 18 gauge needle using helical CT guidance in an outpatient setting. At least 2 whole cores per tumor were obtained. RESULTS: Biopsy material was insufficient for analysis in 3 (3.4%) procedures. Median tumor size of failed biopsies was 3.0 cm. There were 5 (5.6%) biopsies which revealed fibrosis and were considered inconclusive. A benign lesion was found in 14 (15.9%) biopsies. In the 66 biopsies positive for malignancy there were 65 cases of renal cell carcinoma and 1 lymphoma. A total of 62 patients underwent surgery. Biopsy changed tumor management in 42 (47.8%) patients who avoided radical nephrectomy, 13 of whom had a lesion which did not require surgery, 1 with a lymphoma and 28 who were treated with partial nephrectomy. Biopsy accuracy for histopathological tumor type and Fuhrman nuclear grade was 92% and 69.8%, respectively. No substantial morbidity occurred. CONCLUSIONS: Fine needle biopsy of small renal masses could select benign lesions for which observation might be an alternative to surgery. The accuracy of fine needle biopsy in identifying histological tumor type was high. However, biopsy was less accurate in evaluating Furhman grade. Biopsy with helical CT guidance could be a key point in tailored management of small solid renal masses and provide important information to those patients harboring renal masses.     

Defining the complications of cryoablation and radio frequency ablation of small renal tumors: a multi-institutional review

PURPOSE: Ablative treatments (cryoablation or radio frequency ablation) for renal cell carcinoma aim to decrease morbidity by treating renal tumors in situ, eliminating the need for extirpation. These technologies have potential for complications previously unassociated with renal tumor treatment. We identified complications associated with percutaneous and laparoscopic ablative treatment of renal tumors. MATERIALS AND METHODS: Groups at medical centers with reported experience with ablation of renal tumors were invited to participate in this study. Each group submitted retrospective data regarding overall ablative treatment experience and associated complications. For each incident the nature of the complication, its associated morbidity, the necessity and nature of any subsequent interventions, and the final patient outcome were evaluated. Complications were divided into minor and major categories. Data were collected from groups at 4 institutions with a combined experience of 271 cases. Of these cases 139 were cryoablation and 133 were radio frequency ablation. There were 181 procedures performed percutaneously and 90 performed laparoscopically. RESULTS: A total of 30 complications occurred (11.1%) with 5 major (1.8%) and 25 minor (9.2%) complications, and 1 death (0.4%). Overall 26 of the 30 complications (86.7%) were directly attributable to the ablation procedure. The most common complication was pain or paraesthesia at the probe insertion site. CONCLUSIONS: Ablation technologies appear to have a low complication profile when used to treat small renal tumors. The majority of complications are minor and require observation only. Further study and followup are necessary to determine long-term oncological efficacy.     

Imaging characteristics of papillary renal cell carcinoma by computed tomography scan and magnetic resonance imaging

AIM: To analyse the differences in the patterns between clear and papillary renal cell carcinomas using magnetic resonance imaging (MRI) and dual-phase helical computed tomography (CT). METHODS: We examined seven patients with papillary renal cell carcinoma, and six with clear cell carcinoma. The highest attenuation value of tumors in the corticomedullary phase (CMP) and the excretory phase (EP) was measured using the observer-defined region of interest (ROI). MRI consisted of T1-weighted and T2-weighted spin-echo imaging. RESULTS: All five tumors except for one with papillary renal cell carcinoma showed homogenous hypointensity, but all six tumors with clear cell carcinoma showed heterogeneous hyperintensity on their T2-weighted images. In the CMP, the mean CT numbers of the papillary renal cell carcinomas were significantly lower than those of the clear cell carcinomas. The mean enhancement of the papillary renal cell carcinomas in the CMP and the EP was significantly lower than that of the clear renal cell carcinomas. The mean CT numbers of the clear cell carcinomas in the CMP were markedly increased from those on the unenhanced CT; those in the EP were decreased gradually. But the mean CT numbers of the papillary renal cell carcinomas in the EP were still slightly more increased than those in the CMP. The enhancement patterns of the papillary renal cell carcinomas in the CMP and the EP were homogenous, but those of the clear cell carcinomas were heterogeneous. CONCLUSIONS: We can speculate the differential diagnosis from clear to papillary renal cell carcinoma using MRI and dual-phase helical CT.     

Prognostic factors of renal cell carcinoma

PURPOSE: Determination of prognostic factors is essential for the management of renal cell carcinoma. Stage, histological grade and type, and performance status are now well known and commonly used. During the last decade numerous predictors of patient outcome were tested. This review summarizes the most important studies, explores and compares the results, and tries to respond to the question, "Today, what do we expect of clinical, molecular and genetic factors concerning survival of patients with renal cell carcinoma?" MATERIALS AND METHODS: Based on MEDLINE literature searches we comprehensively reviewed the literature on the prognostic factors associated with the tumor, the patient and the treatment. RESULTS: During the last decades numerous factors have been studied but few of them maintained independent significance in terms of overall survival as assessed by multivariate analysis. Results are more often controversial from one series to another. No known molecular or cytogenetic tumor marker has been identified to help diagnose, manage or confirm renal cell carcinoma remission, progression or relapse. CONCLUSIONS: The classical prognostic factors remain histological grade, histological type, performance status, patient age, number and location(s) of metastatic sites, time to appearance of metastases and prior nephrectomy. The only striking advancement during the last few years has been the proven contribution of radical nephrectomy for metastatic disease in patients with good performance status.     

Fat poor renal angiomyolipoma: patient, computerized tomography and histological findings

PURPOSE: We reviewed our experience with fat poor cases of angiomyolipoma. MATERIALS AND METHODS: The records of patients with angiomyolipoma, as determined by pathological study, from 1998 to 2004 were reviewed by recording patient demographics and outcomes. Fat poor cases were defined as the failure of imaging to demonstrate fat in a lesion. Computerized tomography and histological characteristics were assessed. RESULTS: Histologically confirmed angiomyolipoma was found in 15 patients. Multiple lesions were found in 3 of 15 cases (20%). Of these 15 patients who underwent surgery 11 (73%) had unsuspected angiomyolipoma due to absent fat on computerized tomography and they underwent intervention for presumed renal cell carcinoma. Mean age +/- SD in this group was 54 +/- 15 years and 8 of 11 patients (73%) were female, of whom 4 (50%) had uterine fibroids. These lesions were found incidentally in 7 of 11 cases (64%). Operative complications developed in 2 of 11 patients (18%). Average maximal diameter on pathological evaluation was 3.2 +/- 1.3 cm (range 1.5 to 6). Nonenhanced computerized tomography was available in 7 of 11 cases, of which 3 of 7 (42%) showed hyperdense lesions and 4 of 7 (57%) showed isodense lesions. The percent of fat identified per high power field was less than 25% in 12 of 13 fat poor angiomyolipoma lesions (92%) compared to 2 of 4 classic lesions (50%) known to be angiomyolipoma before surgery (p = 0.04). CONCLUSIONS: We suggest that a general definition of fat poor angiomyolipoma should be the failure of imaging to reveal fat within a lesion, thus, making it unsuspected at surgery. A pathological definition should be less than 25% fat per high power field, which to our knowledge is a formerly undefined quantity. Not all cases are hyperdense on nonenhanced computerized tomography. These lesions cannot be reliably identified by imaging and they should be managed like all enhancing renal masses.     

Spoke-wheel-like enhancement as an important imaging finding of chromophobe cell renal carcinoma: A retrospective analysis on computed tomography and magnetic resonance imaging studies

AIM: Little information has been reported with regard to the radiological features of chromophobe cell renal carcinomas (CCRC). The aim of the present study was to identify imaging characteristics which lead to the histological diagnosis of CCRC. METHODS: The imaging findings of computed tomography (CT) and magnetic resonance imaging (MRI) were retrospectively analyzed in 11 patients with CCRC operated on at Tokyo Women's Medical University, Tokyo, Japan. RESULTS: None of the factors studied were significant in distinguishing the two variants, typical and eosinophilic variants. Enhanced CT scans showed a spoke-wheel-like enhancement with a central scar in 3 patients (27%). The radiological patterns were classified into two groups. Seven patients (64%) showed pattern 1 in which: (i) a hypodense to isodense enhancement compared to the renal medulla in the corticomedullary phase during dynamic CT; (ii) an isodense mass compared to the renal medulla in unenhanced CT scan; and (iii) a lobulated appearance were typically observed. Four patients (36%) showed pattern 2 that seemed to be similar to the features of clear cell carcinoma, having an alveolar structure including a hyperdense enhancement in the corticomedullary phase and an inhomogeneous appearance. A spoke-wheel-like enhancement was observed only in patients with pattern 1, and was more clearly demonstrated in larger tumors. CONCLUSIONS: The CT and MRI findings in CCRC patients were not uniform, but it was noted that a spoke-wheel-like enhancement with a central stellate scar, which might have been mistaken for oncocytoma, was one of important findings of CCRC. Tumors demonstrating a spoke-wheel-like enhancement with a central scar should be carefully managed, because they could be malignant.     

Prostate cancer with large glands treated with 3-dimensional computerized tomography guided pararectal brachytherapy: up to 8 years of followup

PURPOSE: We report post-brachytherapy results in patients with cancer in a large prostate. MATERIALS AND METHODS: From June 1, 1994 to June 30, 2000, 331 consecutive patients with a large prostate of 50 to 180 cm.3 (median 69) were treated with 3-dimensional computerized tomography guided brachytherapy. Patient age was 42 to 90 years (median 69). Of these patients 327 were available for followup for 2 to 8 years (median 4.5). Patients were stratified according to risk profile. The high risk group had 1 or more high risk factors (prostate specific antigen [PSA] greater than 20 ng./ml., Gleason greater than 7, stage T2b, T3a or T3b) or 2 intermediate risk factors (PSA 10 to 20 ng./ml. and Gleason 7). The high risk group was further stratified into subgroups with a similar risk profile. The intermediate risk group had only 1 high risk factor (PSA 10 to 20 ng./ml. or Gleason 7). The low risk group had PSA less than 10 ng./ml., Gleason less than 7 and stage T1a, b, c or T2a. A dose of 144 Gy. with 125I or 120 Gy. with 103Pd was achieved in 90% to 100% of the target. A total of 31 patients (9%) had previously undergone transurethral resection and 198 (60%) were treated with 3 months of neoadjuvant androgen ablation. RESULTS: Biochemical disease-free survival was achieved in 90% of the 182 patients at high risk, 96% of the 52 at intermediate risk and 99% of the 93 at low risk. Seven patients (2%) required catheterization during year 1 for urinary retention, 11 (3%) required transurethral prostate resection 1 to 4 years after implantation, 3 patients (1%) had grade 1 or 2 incontinence after repeat transurethral prostate resection and 4 (1%) had grade 3 or 4 rectal complications. CONCLUSIONS: The 3-dimensional computerized tomography guided pararectal permanent implant results in a high level of biochemical control with low morbidity at 2 to 8 years in patients with prostate cancer who have a large prostate. There was less favorable biochemical control in patients with PSA greater than 20 ng./ml., Gleason 7 or greater and seminal vesicle invasion.     

Trends in the incidence of benign pathological lesions at partial nephrectomy for presumed renal cell carcinoma in renal masses on preoperative computed tomography imaging: A single institute experience with 290 consecutive patients

Objective: The aim of this study was to determine trends in the incidence of benign lesions in patients undergoing surgery for suspicious renal masses on preoperative computed tomography scan. Methods: The records of 1065 patients who underwent open consecutive partial nephrectomy (PN) or radical nephrectomy (RN) between January 2001 and December 2008 were reviewed. Patients who underwent PN during the periods 2001–2002, 2003–2004, 2005–2006, and 2007–2008 were assigned to groups 1, 2, 3 and 4, respectively. The frequencies of benign and malignant lesions in these groups were assessed according to size and histology subtypes. Results: The ratio of PN to RN was 12.4%, 18.3%, 24.3% and 37.2% in groups 1, 2, 3 and 4, respectively (P < 0.05). The mean size of resected lesions was 2.6 cm (range 0.8–6.2 cm). Of the 290 cases, histopathology revealed benign findings in 52 (17.9%). Benign pathology was found in three of 18 cases (16.7%) in group 1, seven of 36 cases (19.4%) in group 2, 12 of 63 cases (19.0%) in group 3 and 30 of 173 cases (17.3%) in group 4. There was no significant difference in the frequency of benign histology among groups. Conclusion: PN, as opposed to RN, has shown a rising tendency over time. The frequency of benign pathology findings after PN for suspicious renal masses on preoperative computed tomography imaging has not decreased. Proper management should favor nephron‐sparing surgery for renal lesions if such lesions can be removed satisfactorily with PN.     

Results of computerized tomography guided percutaneous ablation of renal masses with nondiagnostic pre-ablation pathological findings

PURPOSE: Ablative therapy for renal masses has been criticized because the entire tumor cannot be evaluated pathologically after the procedure. Diagnosis depends on imaging findings and the results of percutaneous needle biopsies, which may be nondiagnostic in up to 21% of cases. We determined outcomes in patients undergoing ablation who had nondiagnostic biopsies at the time of the procedure. MATERIALS AND METHODS: A total of 79 patients (88 renal masses) underwent percutaneous computerized tomography guided biopsy and ablation of a renal mass under conscious sedation. Patients with nondiagnostic biopsies were identified and the medical records were reviewed retrospectively. All patients had an enhancing renal mass on preoperative computerized tomography or magnetic resonance imaging and all underwent postoperative contrast imaging to evaluate persistent viable tumor. RESULTS: A total of 19 patients (20 tumors) with nondiagnostic percutaneous biopsy (22.7% or 20 of 88) were included in the study. No serious complications occurred. Tumors were treated with frequency ablation (12) or cryoablation (7). In 17 patients (89.5%) post-procedure imaging confirmed the absence of contrast enhancement at a median followup of 27.3 months (range 3 weeks to 56 months). In 2 cases (10.5%) post-procedure imaging showed a residual renal mass or recurrence with enhancement, suggesting that the original percutaneous biopsy result was false negative. In 1 patient residual tumor was identified on initial post-ablation imaging and the patient underwent laparoscopic partial nephrectomy. In another patient recurrence was diagnosed 30 months after ablation and the patient underwent laparoscopic radical nephrectomy. Although there was a nondiagnostic percutaneous biopsy in each case, pathological findings in the subsequent surgical specimen confirmed renal cell carcinoma. CONCLUSIONS: Nondiagnostic percutaneous biopsy at renal tumor ablation does not obviate the need for standard post-procedure imaging followup. Of patients with nondiagnostic biopsies in this series 10.5% still harbored viable renal cell carcinoma after percutaneous ablation.