Category migration of renal cystic masses with use of gadolinium-enhanced magnetic resonance imaging

The Bosniak renal cyst classification has been accepted by urologists and radiologists as a way of diagnosing cystic renal masses and determining the management approach. We report two cases of a renal cystic mass that showed a category change from category II on the basis of enhanced computed tomography to category IV after further gadolinium-enhanced magnetic resonance imaging. In both cases, the cysts were later confirmed as kidney cancer by pathology.     

Diagnostischer Algorithmus bei zystischen Nierenläsionen

Cystic renal lesions can be classified as either simple or complicated cysts, which might occur as solitary as well as multifocal lesions. The Bosniak classification (I-IV), which characterizes renal cysts on the basis of ultrasound or computer tomographic criteria, is very useful for further decision-making about the therapeutic approach. The method of choice for diagnosis of renal cysts is ultrasound. Besides the conventional B-mode ultrasound, contrast enhanced ultrasound with SonoVue® provides a promising new technique for distinguishing cysts according to the Bosniak classification. This review describes cystic renal lesions with emphasis on the etiology and significance of these pathologies in a methodological comparison of conventional B-mode, contrast enhanced ultrasound and computer tomography.     

Multilocular cystic renal cell carcinoma: clinicopathological features and preoperative prediction using multiphase computed tomography

Study Type – Diagnostic (exploratory cohort) Level of Evidence 2b What’s known on the subject? and What does the study add? Multilocular cystic renal cell carcinoma (MCRCC), defined according to the 2004 WHO classification, has good prognosis, which is not affected adversely by large tumour size or advanced stage. Thus nephron‐sparing surgery is proposed when MCRCC is suspected by preoperative radiologic criteria. The present study confirms the low malignant potential of MCRCC. Additionally, the results of the present study provide a simple, useful criteria using a Bosniak classification and Hounsfield unit on multiphase computed tomography images to differentiate MCRCC from other cystic RCC.

OBJECTIVE

? To analyse the clinicopathological and radiological features of multilocular cystic renal cell carcinoma (MCRCC) and to determine the preoperative factors differentiating MCRCC from other cystic RCC (CRCC).

PATIENTS AND METHODS

? The medical records of 53 patients with complex cystic renal masses evaluated by multiphase computed tomography (CT), surgically removed and confirmed as sporadic RCC were reviewed. ? Of these 53 patients, 23 were classified as having MCRCC and 30 as other CRCCs, defined as RCCs with extensive cystic change or cystic necrosis. ? Another 22 patients were treated for complex cystic renal masses presumed to be RCC and diagnosed as having benign cyst.

RESULTS

? Benign cysts and MCRCCs were significantly more likely to be of Bosniak classification III than other CRCCs (77% vs 61% vs 27%, P= 0.001). ? The mean Hounsfield unit (HU) during the corticomedullary phase (CMP) was significantly higher in other CRCCs, with HU ≥38 having 83% sensitivity and 80% specificity for predicting other CRCCs. ? In a multiple regression model, Bosniak classification and mean HU during CMP were independent factors predictive of other CRCCs. ? In the 41 patients with masses >4 cm in diameter, the combination of Bosniak classification IV and HU ≥38 during CMP showed 63% sensitivity, 96% specificity, 91% positive predictive value and 80% negative predictive value, yielding 2% false‐positive and 15% false‐negative rates.

CONCLUSIONS

? The mean HU during CMP and Bosniak classification can differentiate MCRCC from other CRCCs. ? This could help in selecting an appropriate surgical method, such as nephron‐sparing surgery, for complex cystic renal masses >4 cm.     

Comparación entre tomografía computarizada y resonancia magnética en la evaluación de quistes renales complejos empleando la clasificación de Bosniak

Introduction and objectivesThe Bosniak classification of cystic renal lesions was first published in 1986 based on computed tomography (CT). In the present study, we aimed to investigate the effect of magnetic resonance imaging (MRI) on Bosniak category compared with CT, and to determine how this effect changed the treatment modality in the evaluation of complex renal cysts.Material and methodsData of 144 patients were collected retrospectively. After exclusion criteria, 102 cystic renal lesions with a Bosniak category of at least IIF on CT or MRI between 2013 and 2016 were evaluated by 2 abdominal radiologists. The demographic data, Bosniak category, interobserver agreement, and pathologic data of patients who underwent surgery were recorded.ResultsThe coherence between MRI and CT was 75.5%. The Bosniak classification of 17 patients was upgraded with MRI, and the treatment modality changed in 10 patients, and they underwent surgery. The Bosniak category was downgraded from III to IIF in 6 patients out of 8 whose Bosniak category was downgraded with MRI and the treatment modality changed. Surgery was performed in one patient out of these 6 patients, and the pathology was reported as benign. Progression was detected in the follow-up at month 18 of 1 patient out of 5, and surgery was performed. The pathology was reported as renal cell carcinoma. The pathology result was reported as RCC in 35 (68.6%) patients out of 51 who underwent surgery. Progression was detected in 7 patients out of 51 who were followed up (13.7%), and the pathology results were reported as RCC. The majority of the malignant tumors were low stage and grade.ConclusionsMRI may be successfully used in the evaluation of renal cystic lesions. In particular, the challenging Bosniak IIF and all Bosniak III lesions must be evaluated using MRI before making the decision for surgery. The upgrading of Bosniak category with MRI is more possible compared with CT due to its high-contrast resolution, therefore further studies are required to identify whether it was the cause of overtreatment of Bosniak III lesions.     

An evaluation of Bosniak's radiological classification of cystic renal masses

OBJECTIVE: To determine the clinical usefulness of Bosniak's classification of cystic renal masses, the differentiation of which remains difficult despite significant advances in diagnostic imaging. PATIENTS AND METHODS: The computed tomography (CT) findings of all histopathologically examined cystic renal masses diagnosed at our institution were analysed retrospectively; 35 patients with cystic renal masses were treated between 1986 and 1998. Tissues surgically removed were examined pathologically and the final diagnosis compared with the preoperative CT category of Bosniak's classification. RESULTS: The histopathological examined showed cystic renal cell carcinoma in 21 patients, a benign renal cyst in 12, haemangiosarcoma in one and transitional cell carcinoma in one. Most of the 35 masses (26, 74%) were found incidentally during evaluation for an unrelated disease or a routine health check. All 11 masses of Bosniak category I were benign and one category II mass was malignant. All 10 masses of category III and 12 of category IV were malignant. CONCLUSIONS: Bosniak's classification is useful for differentiating category I, III and IV cystic renal masses. There were too few samples to allow meaningful conclusions to be drawn for category II renal masses. It is critical to differentiate between complicated cysts of category II and III because of the major implications for prognosis and clinical management.     

囊性肾肿物超声造影诊断分析

目的 探讨超声造影对囊性肾肿物诊断价值. 方法 按照影像诊断标准,对29例囊性肾肿物的常规超声、超声造影、增强CT诊断结果进行分级,与最终诊断结果比较,应用受试者工作特征(ROC)曲线进行分析.男15例,女14例,年龄18～63岁.肿瘤位于左肾13例,右肾16例.29例均行常规超声检查后1～3 d行超声造影及增强CT检查. 结果 29例中20例有病理结果,其中恶性18例、良性2例.其余9例中失访1例,8例随访6～12个月,经超声或增强CT检查,病灶无明显变化.常规超声、超声造影与增强CT对囊性肾肿物分级的ROC曲线下面积分别为0.721、0.997、0.997,超声造影与常规超声比较差异有统计学意义(P=0.003),与增强CT比较差异无统计学意义(P=1.000).结论 超声造影对于囊性肾肿物诊断效果优于常规超声,与增强CT相似,可以应用Bosniak诊断系统对囊性肾肿物进行评价.     

Laparoscopic evaluation of indeterminate renal cysts: long-term follow-up

PURPOSE: We present our long-term follow-up of patients who have undergone laparoscopic evaluation for their indeterminate renal cysts, specifically reporting those patients who were found to have cystic renal-cell carcinoma (RCC) and assessing the safety and efficacy of the procedure. PATIENTS AND METHODS: Fifty-seven patients with indeterminate renal cysts (28 Bosniak category II and 29 Bosniak category III) underwent laparoscopic evaluation between July 1993 and July 2000. A transperitoneal laparoscopic localization and aspiration of the cyst, cytologic analysis, and biopsy of the cyst wall and base were performed. A total of 11 patients were found to have cystic RCC. Patients with malignancy have been followed for a mean of 40 months (range 6-70 months), and five patients had 5 years or more of follow-up. RESULTS: Eleven patients (19% of the total) were found to have cystic RCC. Three of these patients had Bosniak category II cysts, and eight had category III cysts. All tumors were low grade (I or II), and the stages were T1-2, Nx-0, M0. There has been no evidence of laparoscopic port site or renal fossa tumor recurrence, local recurrence, or metastatic disease to date in these patients. There is no cancer-specific mortality. CONCLUSIONS: Long-term follow-up indicates that laparoscopic evaluation of indeterminate renal cysts is not associated with an increased risk of port site or retroperitoneal or peritoneal recurrence of RCC. It may save a patient from undergoing open surgery and should be considered as a diagnostic option for patients with indeterminate renal cysts.     

A simple renal cyst invaded by infiltrating urothelial carcinoma mimicking a Bosniak Class IV renal cyst

We report a 79-year-old woman with a left side simple renal cyst invaded by infiltrating urothelial carcinoma mimicking a Bosniak Class IV renal cyst. Computerized tomography has high accuracy for the diagnosis of renal cysts and urothelail carcinoma. But, in this case it was still difficult to distinguish a simple renal cyst with infiltrating urothelial carcinoma invasion from a Bosniak Class IV renal cyst on CT scan. The management of a Bosniak Class IV renal cyst and urothelail carcinoma is totally different. Therefore, we performed a left side nephroureterectomy. This patient will have regular follow-up with cystoscopy every 3 months for the first 2 y, every 6 months for the next 2 y, and then annually thereafter.     

Evaluation of complicated renal cyst: a comparison of CT and MR imaging]

We report 12 cases of renal cystic lesions that could not be diagnosed preoperatively. Sonography, computed tomography (CT), magnetic resonance (MR) imaging, and angiography were performed in all cases. Angiography was not helpful in evaluating cystic lesions, because all cystic lesions were hypovascular or avascular within the cystic mass. CT was useful in depicting the fine structural abnormalities, and especially bolus-contrast CT study was useful in the differentiation of cystic renal cell carcinoma from simple renal cyst. However, there were 5 false positive cases. MR imaging is superior to CT in distinguishing a hemorrhagic cyst or multiloculated cystic mass. In conclusion, CT is currently the primary imaging modality for evaluating complicated renal cysts, and surgical exploration is warranted for the undiagnosed cystic lesion by CT. However, MR imaging also has an important role in detecting the benign complicated cyst. Therefore if complicated cyst is thought to be benign by MR imaging, parenchyma-sparing surgery should be considered preoperatively.     

Contrast-enhanced ultrasound assessment of complex cystic lesions in renal transplant recipients with acquired cystic kidney disease: preliminary experience

We prospectively studied the potential value of contrast-enhanced ultrasound (CEUS) to characterize complex acquired cystic kidney disease (ACKD) or suspected solid renal masses, avoiding the risk of inducing acute kidney injury in 138 renal transplant recipients by contrast-enhanced computed tomography (CT). Forty-three cases (31%) had ACKD; 15 ACKD patients (35%) showed suspicious or nondiagnostic ultrasound. The latter subgroup underwent CEUS and, if the suspicion was confirmed, a contrast-enhanced CT. Thirty five lesions were identified in the 15 patients studied by CEUS. According to the Bosniak classification, 27 cysts were type I (BI), four type II (BII), two type III (BIII) with enhancement at the level of thickened septa; we also identified two solid enhancing lesions (BIV). We followed the BI and BII lesions with serial CEUS, while the remaining four cases underwent contrast-enhanced CT showing two solid lesions and two complex cysts with contrast enhancement in the septea. The four patients underwent surgical resection yielding three renal cell carcinomas one papillary carcinoma as the pathological findings. This preliminary study characterized solid nodules and BIII lesions for further evaluation by CT. CEUS seems to correctly characterize BI and BII cysts that are not clearly defined by standard ultrasound.     

Extensively Cystic Renal Neoplasms in Adults (Bosniak Classification II or III) – Possible “Common” Histological Diagnoses: Multilocular Cystic Renal Cell Carcinoma,Cystic Nephroma,and Mixed Epithelial and Stromal Tumor of the Kidney

Objective(s): To give an algorithm for resolution of extensively cystic renal neoplasms, preoperatively classified in the Bosniak classification as a category II and III. Methods: From 1991 to 6/2004, 701 patients with 727 renal tumours were surgically treated at our hospital. Extensively cystic tumours were found in 10 cases. Extensively cystic tumours were defined as multicystic tumours without any solid nodules visible neither on CT, nor grossly in the specimen at operation (the Bosniak classification type II or III). Results: Seven multilocular cystic renal cell carcinomas, three mixed epithelial and stromal tumour of the kidney and one cystic nephroma were diagnosed on histology. Conclusion(s): Extensively cystic renal tumours classified as the Bosniak type II or III correspond histologically to the entities mentioned above (multilocular cystic renal cell carcinoma, cystic nephroma, mixed epithelial and stromal tumour of the kidney). These entities cannot be distinguished one from another on preoperative imaging studies. A preoperative biopsy and intra-operative frozen-section analysis do not lead to a correct diagnosis in many cases. Fortunately, the operative strategy is the same for all these tumours. In such cases, the nephron sparing surgery is indicated, whenever technically feasible, as almost all extensively cystic renal tumours have a good prognosis.     

"Indeterminate" cystic lesion of the kidney partially lined by small cells with clear cytoplasm--malignant or benign?

Complex renal cysts, which present radiographically as "indeterminate for malignancy" (Bosniak category III), can prove challenging both pathologically and clinically. We report a case of a renal cyst that, by standard radiographic and histologic criteria, should have been diagnosed as a malignant cystic renal cell carcinoma. However, the cytogenetic profile appeared more closely consistent with cystic renal adenoma or low-grade papillary renal cell carcinoma--tumors with limited metastatic potential. We postulate that other, similarly complex, renal cysts might also be more precisely defined by meticulous histopathologic examination, supported by cytogenetic study.     

Pathological characteristics and radiographic correlates of complex renal cysts

ObjectivesTo characterize pathological and cancer-specific outcomes of surgically resected cystic renal tumors and to identify clinical or radiographic features associated with these outcomes.Methods and materialsAll patients at our institution who underwent radical or partial nephrectomy for complex renal cystic masses between 2004 and 2011 with available computed tomographic imaging were included. The Bosniak score was determined, as were 10 specific radiographic characteristics of renal cysts in patients with preoperative imaging available for review. These characteristics were correlated with cystic mass histopathology. Recurrence-free survival after surgery was determined.ResultsOverall, 133 patients underwent renal surgery for complex cystic lesions, 89 (67%) of whom had malignant lesions. Malignancy risk increased with Bosniak score (P≤0.01) and presence of mural nodules (P = 0.01). Most (63%) malignancies demonstrated clear cell histology. The papillary renal cell carcinomas (25%) exhibited lower enhancement levels (P = 0.04) and were less often septated (P<0.01). Of the malignancies, 79% were low stage (pT1), and 73% were Fuhrman grade 1 or 2. Large cyst size was associated with advanced tumor stage (P = 0.05). Neither Bosniak score nor any other radiographic parameter was associated with Fuhrman grade. In 70 patients with a median follow-up of 43 months, only 1 (1.4%) developed disease recurrence.ConclusionsMost cystic renal malignancies are low-stage, low-grade lesions. Papillary renal cell carcinomas account for nearly a quarter of cystic renal malignancies and have unique radiographic characteristics. Disease recurrence after surgical resection is rare. These findings suggest an indolent behavior for cystic renal tumors, and these lesions may be amenable to active surveillance.     

Magnetic resonance imaging as an adjunct diagnostic tool in computed tomography defined Bosniak IIF–III renal cysts: a multicenter study

Introduction

CT imaging is the standard examination for renal cystic lesions and defines the Bosniak category, which dictates further management. Given that Bosniak II/IIF/III renal cystic lesions can potentially harbor renal cell carcinoma (RCC), additional diagnostic modalities may be required in management decision making.

Aim

To determine the value of additional magnetic resonance imaging in CT-defined Bosniak IIF–III renal cystic lesions.

Materials and methods

This a multicenter retrospective study of 46 consecutive patients, diagnosed with cystic renal lesions between 2009 and 2016. The inclusion criteria were: (1) cystic renal lesion classified as Bosniak IIF–III on CT, (2) a subsequent MRI examination, and (3) documented outcome via surgery for cystic renal mass or follow-up.

Results

46 patients (35 males, 11 females) were included. The mean size of the cystic lesion was 3.92 cm (0.7–10 cm). According to the CT findings, Bosniak IIF and III were found in 12 (26.1%) and 34 (73.9%) cases. Reclassification of Bosniak category was done after MRI examination in 31 cases (67.4%). An upgrade rate of 58.7% (27 cases) to a higher category was made, while the downgrade rate to a lower category was achieved in 4 cases (8.7%). As a result, significant therapeutic management change was made in 12/31 patients (38.7%), of whom 8 underwent subsequent surgery.

Conclusion

MRI study may reduce the use of Bosniak IIF category (in comparison with CT), which has a direct impact on therapeutic management (surgery vs. surveillance) in a significant proportion of patients.

     

BosniakⅡ~Ⅳ级肾囊性占位临床与病理学特点分析简

目的 探讨Bosniak Ⅱ-Ⅳ级肾囊性占位临床与病理学特点。方法 回顾性分析上海交通大学医学院附属仁济医院从2008年1月至2012年12月CT诊断为囊性肾脏占位（BosniakⅡ、ⅡF、Ⅲ、Ⅳ）的170例患者的病例资料,其中Ⅱ级囊肿73例,ⅡF级囊肿34例、Ⅲ级囊肿38例、Ⅳ级囊肿25例。男105例,女65例;年龄20-85岁,平均（56±14.2）岁;病灶位于左侧87例,右侧66例,双侧17例。80例接受手术治疗的患者中,Ⅱ级囊肿18例,ⅡF级囊肿8例,Ⅲ级囊肿30例,Ⅳ级囊肿24例;行腹腔镜肾囊肿去顶减压术25例,腹腔镜肾部分切除术15例,腹腔镜根治性肾切除术7例,开放肾癌根治术6例,开放肾部分切除术27例。其余90例进行了影像学的随访。分析不同分型囊性肾脏占位的良恶性比例、病理学特点、随访结果。结果 手术病例中Ⅱ级囊肿恶性病例为1例（5.6%）,ⅡF级1例（12.5%）,Ⅲ级16例（53.3%）,Ⅳ级21例（87.5%）,组间比较有明显统计学差异（P＜001）。术后病理结果：恶性肿瘤共39例（透明细胞癌31例,乳头状癌8例）,Fuhrman分级均为Ⅰ级。良性病例共41例（单纯囊肿26例,囊肿伴出血3例,囊肿伴感染5例,囊性肾瘤4例,错构瘤3例）。术后患者随访时间为6-65月,平均随访25月,恶性病例均无发生局部复发或远处转移。影像学随访病例中BosniakⅡ级为55例,ⅡF级26例, Ⅲ级为8例,Ⅳ级为1例,随访时间为6-64月,其中1例Ⅱ级（1.8%）进展至ⅡF级,其余病例均未进展。结论 Ⅱ、ⅡF级囊肿恶性率较低、进展缓慢建议定期随访,而Ⅲ、Ⅳ级恶性率较高应积极手术处理。但由于囊性肾癌组织学分级往往较低,其术后复发、进展及远处转移率较低,保肾手术是首选的治疗方案。     

Complex renal cyst. Laparoscopic treatment

The difference between the simple renal cysts, that doesn't require surgical treatment, and those that need it, sometimes is difficult. The laparoscopic surgical treatment (laparoscopic cyst decortication -laparoscopic partial nefrectomy or radical laparoscopic nefrectomy) its becoming the gold standard technique, recommending this procedure in Bosniak cyst type III or IV, and in the symptomatic renal cyst type I/II and in any patients with Bosniak cyst renal II. We present a case report in which a renal cell carcinoma was found after laparoscopic cyst decortication of Bosniak cyst type II with laparoscopic radical nefrectomy posteriorly.     

Renal cell carcinoma and end stage renal disease

PURPOSE: Patients with ESRD secondary to acquired renal cystic disease have been reported to have a higher incidence of RCC than the general population. We examined the clinical and pathological significance of incidental renal masses in patients with ESRD. MATERIALS AND METHODS: From January 1994 to July 2000, 852 consecutive patients with ESRD who were being considered for renal transplantation at University of Mississippi Medical Center were evaluated with renal ultrasound as part of assessment for possible kidney transplantation. Those patients with ultrasound suspicious for a malignant renal lesion were further evaluated with CT of the abdomen with and without intravenous contrast medium. Any patient with CT findings suspicious for RCC was recommended to undergo radical nephrectomy before kidney transplantation. RESULTS: A total of 19 patients had CT criteria for a possible malignant renal lesion. Seven patients had Bosniak class 3 renal cysts and 12 patients had solid, enhancing renal masses. Of the patients 17 underwent radical nephrectomy. On pathological examination 14 patients had RCC with a 1.64% prevalence in the population screened. Mean Fuhrman nuclear grade in our patients was 2.45. CONCLUSIONS: RCC in patients with ESRD are of clinical significance, considering the size, grade, histology and pathological stage of these tumors. The higher prevalence of clinically significant RCC in patients with ESRD as well as the risk of cancer progression while patients are on immunosuppressive medications justifies screening for RCC in patients with ESRD who are awaiting renal transplantation.     

Laparoscopic deroofing of a renal cyst: the hidden invasion

Cysts of the kidney usually originate from the renal parenchyma after tubule obstruction; rarely pyelocalyceal cysts occur, originating from transitional urothelium. Neoplasia is a rare but possible complication. A 45-year-old man was found to have a cyst related to the right kidney. Computed tomography demonstrated minimal calcification in the wall (Bosniak II). Symptom-relieving percutaneous drainage yielded clear fluid; resultant cytology was negative. After rapid reaccumulation, laparoscopic deroofing was performed. No communication within the renal pelvis was detected however histology revealed transitional cell carcinoma. An open radical nephroureterectomy was performed; adjuvant chemotherapy was given. Three previous cases of malignancy in a pyelocalyceal cyst have been reported. This is the first reported after laparoscopic deroofing of a cyst. Despite widespread use of the Bosniak renal cyst classification, the management of category II cysts remains contentious. This case should serve as a warning to clinicians that seemingly benign cysts of the kidney may harbor underlying neoplasia. Intraoperative frozen section should be considered in all cases where preoperative imaging suggests Bosniak II classification.     

Laparoscopic management of renal cystic disease

Laparoscopic management of renal cystic disease is a highly effective, safe, and minimally invasive alternative to open surgery and antegrade or retrograde endoscopic procedures. Simple renal cysts can be accessed either transperitoneally or retroperitoneally. Almost all studies of the laparoscopic approach have demonstrated great satisfaction in terms of efficacy, minimal complications, operative time, minimal blood loss, hospital stay, recuperation, and cosmesis over other methods of treating renal cysts. Laparoscopic unroofing of peripelvic cysts is more challenging owing to their proximity to hilar vessels and the collecting system. Such surgery should be considered an advanced laparoscopic procedure. Access may be achieved either transperitoneally or retroperitoneoscopically. The basic principle of adequate exposure is essential for effective treatment. If the cyst is not completely excised, the surgeon must fulgurate the edge and tack perirenal fat in the residual cyst cavity to prevent recurrence and facilitate drainage. Laparoscopic evaluation of complex cysts seems to be sound. The results are promising, and follow-up does not show any increase in peritoneal seeding, tract recurrence, or distant metastases in the small number of neoplasms diagnosed at laparoscopy. Nevertheless, more studies are required with long-term follow-up. Bosniak type IV renal cysts or malignancy in renal cysts can be managed by laparoscopic radical nephrectomy with either access. Laparoscopic cyst marsupialization in patients with ADPKD is the latest emerging indication for laparoscopy in renal cystic disease. This procedure not only effectively reduces pain in some patients but also improves hypertension and stabilizes renal function, delaying renal replacement therapy. Long-term follow-up and further evaluation are needed.     

Complex renal cystic masses: current standards and controversies

Bosniak classification system is the only preoperative diagnostic tool that has proven its efficiency in the management of complex renal cystic masses. However, it is reader dependent, despite its clear definition of each category. The overall incidence of malignancy in each category did not change significantly over the past 20 years. Current limitations are interobserver variability among readers and a fact that a significant proportion of Bosniak III masses have benign character. The goal is to depict these masses preoperatively and spare the patients of unnecessary surgeries, which raises the question: What particular findings will help in differentiating a Bosniak IIF lesion from a Bosniak III lesion? Do we need to define critical variables that could improve accuracy of Bosniak classification by developing a future nomogram or risk calculator? Some radiologists and urologists erroneously tend to group Bosniak II and IIF in one category and observe them regularly. It seems that radiographic growth itself is insufficient factor for intervention. The change of internal architecture and presence of enhancement play the most important role in depicting malignant lesions during the time frame of active surveillance.