Cystic renal masses: accurate Bosniak classification requires adequate renal CT

OBJECTIVE: The objective of this study was to assess the practical usefulness of the Bosniak classification system for separating surgical from nonsurgical cystic renal masses in a large number of patients examined with properly performed renal CT. The study included only patients whose scans were technically adequate to allow proper assignment of the lesion to a category. MATERIALS AND METHODS: The scans of 109 patients were gathered from two large teaching institutions both prospectively and retrospectively, yielding a total of 116 analyzable renal cystic lesions. Eighty-two masses were resected from 77 of these patients, retrospectively categorized by two experienced uroradiologists using the Bosniak classification system, and correlated with pathology reports. A second group of 34 lesions in 32 patients with atypical cysts was followed up prospectively for periods ranging from 3 months to 10 years. RESULTS: The results were similar for the two institutions: 15 resected categories I and II lesions were correctly identified as benign, and all 18 category IV lesions were malignant. Twenty-nine (59%) of 49 pooled category III masses were malignant. No malignancies have been identified in the prospectively monitored group of patients. CONCLUSION: Our results are compared with earlier, smaller series and support those that show that the Bosniak classification system is useful in separating lesions requiring surgery from those that can be safely followed up, provided proper CT techniques are used.     

Cystic renal masses: Usefulness of the bosniak classification

To determine the usefulness of the Bosniak classification of cystic renal masses, the computed tomographic (CT) and ultrasound findings of 16 pathologically proven cystic renal masses were retrospectively reviewed. All imaging studies were reviewed and categorized utilizing the Bosniak classification without knowledge of the final pathologic diagnosis. There were no category I lesions (classical simple cyst), four category II (minimally complicated), seven category III lesions (more complicated), and five category IV lesions (probable malignant). All category II lesions were benign, all category IV lesions were malignant. Of the seven category III lesions, three were benign and four were malignant. We conclude that the Bosniak classification is extremely useful in the management of cystic renal masses. The opinions expressed herein are those of the authors and are not to be construed as official or as reflecting the views of the Uniformed Services University of the Health Sciences, the Department of Defense, or the United States Navy     

Assessment of cystic renal masses based on Bosniak classification: comparison of CT and contrast-enhanced US

OBJECTIVES: To compare retrospectively the imaging features of computed tomography (CT) and contrast-enhanced US (CEUS) imaging for the assessment of cystic renal masses using the Bosniak classification system. MATERIALS AND METHODS: The CT and CEUS images of 31 pathologically confirmed cystic renal masses in 31 patients were retrospectively analyzed for septa numbers, wall and/or septa thickness, enhancement degree, and for the presence of a solid component by consensus between two radiologists using the Bosniak classification. Diagnostic accuracies of CT and CEUS for malignant cystic tumor were calculated and compared using McNemar test. RESULTS: Diagnostic accuracies of CT and CEUS for malignant renal tumor were 74% and 90%, respectively, but there were not statistically different (P>0.05). CEUS and CT images showed same Bosniak classification in 23 (74%) lesions and there were differences in 8 (26%) lesions, all of which were upgraded by CEUS; one lesion from I to IV, two lesions from II to IV, two lesions from IIF to III, and three lesions from III to IV. CEUS images depicted more septa in 10 (32%) lesions, more thickened wall and/or septa in 4 (13%) lesions, and stronger enhancement in 19 (61%) lesions. Moreover, for six lesions, solid component was detected by CEUS but not by CT. CONCLUSION: CEUS might better visualize septa number, septa and/or wall thickness, solid component and the enhancement of some renal cystic masses than CT, resulting in upgrade of Bosniak classification and affecting their treatment plan.     

Evaluation of cystic renal masses: comparison of CT and MR imaging by using the Bosniak classification system

PURPOSE: To compare computed tomography (CT) and magnetic resonance (MR) imaging in the evaluation of cystic renal masses by using the Bosniak classification system. MATERIALS AND METHODS: Images of 69 renal masses in 59 patients (38 men, 21 women; mean age, 60.4 years; range, 30-86 years), who had undergone both CT and MR imaging examinations within 1 year (average, 60.5 days; range, 0-356 days), were retrospectively analyzed by two radiologists in consensus. For each lesion, images were compared for thickness of wall and septa, number of septa, and presence of enhancement. Each mass was categorized (Bosniak classification) first on CT images and then on MR images, and results were compared. Pathologic correlation was available in 25 lesions. RESULTS: On CT images, there were 15 category I, 16 category II, 10 category IIF, 19 category III, and nine category IV lesions. Findings on CT and MR images were similar in 56 (81%) lesions; in 13 (19%) lesions, there were differences. In eight (12%) lesions, MR imaging depicted more septa than did CT, which resulted in an upgrade of the classification at MR imaging in two cases. In seven (10%) lesions, MR imaging depicted increased wall and/or septa thickness compared with CT, resulting in a classification upgrade in six cases. Three lesions had both increased numbers of septa and thickening of the wall and/or septa. In two (3%) lesions, enhancement characteristics at CT and MR imaging were different. One of these lesions also had an increased number of septa. Overall, MR imaging results led to a cyst classification upgrade of seven lesions, from category II to IIF (n = 2), IIF to III (n = 3), or III to IV (n = 2). Pathologic correlation in 25 lesions revealed 20 malignant and five benign lesions. CONCLUSION: CT and MR imaging findings were similar in the majority of cystic renal masses. In some cases, however, MR images may depict additional septa, thickening of the wall and/or septa, or enhancement, which may lead to an upgraded Bosniak cyst classification and can affect case management.     

Diffusion-weighted magnetic resonance imaging in evaluation of primary solid and cystic renal masses using the Bosniak classification

Purpose

Our purpose was to determine whether quantitative diffusion-weighted MR imaging (DWI) could be used in discrimination of benign and malignant primary solid and cystic renal tumors.

Materials and methods

A total of 105 consecutive patients with renal masses and 30 healthy controls were enrolled in this prospective study. Dynamic contrast enhanced routin renal images and DWI (with b factors of 0, 500 and 1000 s/mm²) was performed at 1.5 T unit. Renal masses were divided into two groups as cystic or solid and all cystic lesions were prospectively assigned to a Bosniak classification number. The median apparent diffusion coefficient (ADC) values along with b 500 and 1000 signal intensities of normal kidneys, solid components of mixed renal masses and total of cystic lesions were calculated.

Results

The mean ADC value of normal renal parenchyma in control group was 2.18 ± 0.13 × 10⁻³ mm²/s. Solid renal tumors had significant lower ADC values (median: 1.16 ± 0.27 × 10⁻³ mm²/s), in contrast to cystic tumors (median: 2.73 ± 0.44 × 10⁻³ mm²/s). The mean ADC value of the Bosniak Category I cysts was significantly higher (3.09 ± 0.14 × 10⁻³ mm²/s) than normal renal parenchyma (p < 0.01). A statistical significance was achieved between the signal intensity of Bosniak Category I and Category II–III cysts with b 1000 (p < 0.05). Among the different histologic subtypes of renal cell carcinoma, the mean ADC value of chromophobe cell carcinoma (1.41 ± 0.09 × 10⁻³ mm²/s) was significantly higher than that of papillary cell carcinoma (0.90 ± 0.16 × 10⁻³ mm²/s) and clear cell carcinoma (1.23 ± 0.13 × 10⁻³ mm²/s).

Conclusion

Accurate assessment of renal masses is important for establishing whether tumors require surgical intervention or not. While MRI is a useful modality as an investigative tool for diagnosing, characterizing and staging renal masses, DWI contributes additional value by promising differentiation benign from malignant renal tumors, even histologically subtyping of renal cell cancer.     

The Bosniak renal cyst classification: 25 years later

In the past 25 years, there have been continuous advances in the diagnosis of disease throughout the body owing to the introduction of new technology and the experience gained with its use. However, the imaging and evaluation of complicated cystic lesions of the kidneys frequently remains a difficult problem. The classification of renal cystic lesions suggested 25 years ago, now referred to as the Bosniak renal cyst classification, remains pertinent to the diagnosis and management of these difficult-to-diagnose complicated cystic masses.     

Assessment of cystic renal masses in children: Comparison of multislice computed tomography and ultrasound imaging using the Bosniak classification system

To retrospectively compare contrast-enhanced multislice computed tomography (MSCT) and ultrasound (US) imaging for the assessment of cystic renal masses in children using the Bosniak classification system. Twenty-two consecutive patients (age 1 month to 5.2 years, mean 2.4 years) with 24 cystic renal masses (7 benign, 17 malignant) pathologically confirmed after surgical resection underwent both MSCT and US imaging, and were retrospectively analyzed using the Bosniak classification. A senior and a junior radiologist retrospectively and independently reviewed imaging findings. The sensitivity, specificity, positive predictive value and negative predictive values of MSCT and US were assessed using diagnostic statistics. The statistical significance of differences was determined by the McNemar test. Both radiologists accurately predicted lesions of categories I and IV with the Bosniak classification using MSCT and US. All masses classified as Bosniak classes I and II were proven to be benign, and all malignant lesions were correctly characterized in all cases both on ultrasound images and on the contrast-enhanced CT (CECT) images. Two benign multilocular cystic nephromas and one multicystic dysplastic kidney were classified into category III or even IV based on the classification scheme because of their multilocular nature and thick septation. The diagnostic accuracy of CECT was slightly better than ultrasound (CECT vs. US: senior reader, 92% vs. 88%; junior reader, 88% vs. 83%). However, there was no statistically significant difference between the two sets (p > 0.05). The two radiologists had perfect inter-observer agreement on the two modalities. Both MSCT and US provide highly accurate diagnosis for the malignant renal cystic masses in children using the Bosniak classification system, but assessment of benign masses still needs improvement. We would recommend US is the best screening modality in Bosniak I and II, In Bosniak III and IV, MSCT are first the choice.     

Bosniak分级在MRI诊断肾脏复杂囊性病变中的应用

目的：探讨Bosniak分级在MRI诊断肾脏复杂囊性病变中的应用.方法：41例经病理证实的肾脏复杂囊性病变,恶性28例,良性13例.观察其MRI表现,进行Bosniak分级.并与病理及手术结果进行对照.结果：恶性、良性两组分隔数量大于4的病变比例分别为67.9%和23.1%,差异有显著性意义（P=0.007）.恶性组中囊壁或分隔增厚的病变中88.2%可见不规则增厚,明显高于良性组的28.6%（P=0.009）.9例病变实性成分大于25%,6例有假包膜征象,病理证实均为恶性.恶性、良性组中病变有明显强化分别占85.7%扣23.1%,差异有显著性意义（P〈0.001）.强化征象诊断恶性的敏感度、特异度和符合率分别为82.6%、76.9%和82.9%.恶性组Ⅱ～Ⅳ级病变和Ⅱ～ⅡF级病变比例分别为89.3%和10.7%,良性组为30.8%和69.2%,差异有显著性意义（P〈0.001）.结论：增强仍是MRI Bosniak分级和良性鉴别的最可靠征象,囊壁和分隔的增厚、实性成分比、分隔数量及假包膜等征象也有重要诊断价值.     

Complex cystic renal masses: Comparison of cyst complexity and Bosniak classification between 1.5 T and 3 T MRI

Purpose

To retrospectively compare perceived complexity and Bosniak cyst classification of cystic renal lesions between 1.5 T and 3 T MRI.

Methods

33 cystic renal lesions in 26 patients that underwent contrast-enhanced MRI at both 1.5 T and 3 T within a 12 month span were included. Two radiologists (R1, R2) independently assessed lesions, unaware of field strength, in terms of number of septations, septal thickening, mural thickening, presence of mural nodule, and Bosniak cyst category. Scores were compared between field strengths for each lesion.

Results

R1 observed increases in septal number, septal thickening, mural thickening, and presence of mural nodule at 3 T in 8, 7, 4, and 2 lesions, and at 1.5 T in 3, 3, 2, and 0 lesions, respectively; R2 observed increases in septal number, septal thickening, mural thickening, and presence of mural nodule at 3 T in 3, 4, 3, and 0 lesions, and at 1.5 T in 2, 0, 0, and 0 lesions, respectively. R1 provided higher Bosniak category at 3 T in 9 cases and at 1.5 T in 4 cases; R2 provided higher Bosniak category at 3 T in 4 cases and at 1.5 T in 0 cases. Higher scores at 3 T than 1.5 T were associated with differences in advised clinical management in 7/9 cases for R1 and 4/4 cases for R2.

Conclusion

There was an overall tendency for both readers to upgrade cyst complexity and Bosniak cyst category at 3 T than 1.5 T, which impacted advised management. Thus, we suggest that serial MRI evaluation of cystic renal lesions be performed at constant field strength.     

MR classification of renal masses with pathologic correlation

To perform a feature analysis of malignant renal tumors evaluated with magnetic resonance (MR) imaging and to investigate the correlation between MR imaging features and histopathological findings. MR examinations in 79 malignant renal masses were retrospectively evaluated, and a feature analysis was performed. Each renal mass was assigned to one of eight categories from a proposed MRI classification system. The sensitivity and specificity of the MRI classification system to predict the histologic subtype and nuclear grade was calculated. Subvoxel fat on chemical shift imaging correlated to clear cell type (p < 0.05); sensitivity = 42%, specificity = 100%. Large size, intratumoral necrosis, retroperitoneal vascular collaterals, and renal vein thrombosis predicted high-grade clear cell type (p < 0.05). Small size, peripheral location, low intratumoral SI on T2-weighted images, and low-level enhancement were associated with low-grade papillary carcinomas (p < 0.05). The sensitivity and specificity of the MRI classification system for diagnosing low grade clear cell, high-grade clear cell, all clear cell, all papillary, and transitional carcinomas were 50% and 94%, 93% and 75%, 92% and 83%, 80% and 94%, and 100% and 99%, respectively. The MRI feature analysis and proposed classification system help predict the histological type and nuclear grade of renal masses.     

Cystic masses of the pancreas.

Although the pseudocyst is the most common cystic mass of the pancreas found at imaging studies, radiologists should be aware of the multiple disease processes that can manifest in a similar manner. This article reviews these other entities by category of the origin of the mass, including congenital, inflammatory, and neoplastic. Computed tomography, ultrasound, and magnetic resonance imaging studies are presented, and, although the considerable overlap of imaging features makes it generally impossible to render a specific diagnosis, combining the findings from these modalities is helpful in formulating a differential diagnosis. Because a cystic mass of the pancreas is not always a pseudocyst, percutaneous drainage should be followed by cytologic analysis of the aspirate. A biopsy of the wall of the cystic mass may also be necessary.     

Cystic masses of the spleen: radiologic-pathologic correlation.

Many focal splenic lesions may appear to be cystic at cross-sectional imaging. In this article, the following types of cystic splenic masses are discussed: congenital (true cyst), inflammatory (abscesses, hydatid cyst), vascular (infarction, peliosis), posttraumatic (hematoma, false cyst), and neoplastic (hemangioma, lymphangioma, lymphoma, metastasis). The key findings at ultrasound, computed tomography, and magnetic resonance imaging can be correlated with underlying gross and microscopic pathologic findings. Although tissue sampling is still required in many cases to yield a definitive diagnosis, recognition and understanding of the spectrum of imaging and pathologic features of these lesions often help narrow the differential diagnosis.     

CT-guided biopsy of indeterminate renal cystic masses (Bosniak 3 and 2F): accuracy and impact on clinical management

The purpose of this study was to determine ability of cyst aspiration and core biopsy to differentiate malignancies, and benign lesions needing intervention from benign complex cysts in the group of Bosniak 2F and 3 renal cysts. One hundred ninety-nine indeterminate complex renal cysts were biopsied under CT or US guidance using a coaxial system (19-G sheath, 20- or 21-G Chiba or Franseen or 18-G spring biopsy needle). Cytology, amylase, lipase, LDH, fat, protein, urea nitrogen, creatine, and culture and sensitivity were assessed in all patients, histopathology in 116, and flow cytometry in 32. In 179 patients (87.9%) a definitive diagnosis was made; in 20 the specimen was inadequate. Twenty of 28 malignancies were correctly diagnosed (sensitivity 0.71); 27 of 31 benign lesions needing intervention (sensitivity 0.87) and 128 of 140 benign complex cysts (sensitivity 0.91). All inconclusive biopsies were explored revealing six malignancies. There were four CT biopsy misdiagnoses: two renal cell carcinomas; one angiomyolipoma; and one abscess. Guided cyst puncture aspiration and core biopsy significantly altered management of Bosniak 3 and 2F renal cysts obviating surgery or invasive procedures in 70% of the patients with an affirmed diagnosis of benign complex cyst and rendering timely surgical and other interventions in the remaining patients. Long-term follow-up (mean 5.6 years) revealed no further misdiagnosis.     

Cystic masses of the knee: magnetic resonance imaging findings

Cystic masses of the knee comprise a diverse group of pathologic entities ranging from simple cysts to complications of underlying disease to tumors. Although their presentations may be similar, the appropriate treatment and patient management can differ greatly. In this article, we review radiographic and magnetic resonance imaging characteristics of both common and uncommon cystic masses of the knee.     

多层螺旋CT结合Bosniak分级在肾囊性肿物诊断中的价值

目的 评价多层螺旋CT(MSCT)结合Bosniak分级对肾囊性肿物的诊断价值. 资料与方法 回顾性分析经手术、病理证实的109例患者共129个肾囊性占位术前MSCT的影像表现,并根据肾囊性占位的CT征象对其进行Bosniak分级;将MSCT的Bosniak分级结果与病理进行对照分析,判断各个级别中恶性囊肿的发生率;采用logistic回归分析预测Ⅰ～Ⅳ级中恶性肾囊肿的可靠CT征象. 结果 129个囊性肿物中,17个为恶性,112个为良性.对129个Ⅰ~Ⅳ级囊性病灶的CT特征进行logistic回归分析,结果显示实性成分强化是预测恶性肾囊肿的唯一可靠征象. 结论 高分辨CT结合Bosniak分级对大部分囊性肿物能够准确诊断;实性成分强化是预测恶性囊性肿物的唯一可靠征象.     

Bosniak分级在肾脏囊性病变MSCT诊断中的价值

目的 探讨Bosniak分级在肾脏囊性病变的MSCT诊断中的应用价值,提高对肾脏囊性占位的影像学特点的认识.方法 回顾近年来本院经手术、病理证实的肾脏囊性占位共42例,全部病例经过MSCT检查,结合Bosniak分级进行分类,并与病理诊断对照分析.结果 42例肾脏囊性肿物中,BosniakⅠ级4例均为良性,Ⅱ级11例中有1例为恶性,ⅡF级4例中1例为恶性,Ⅲ级13例中5例为恶性,Ⅳ级10例中9例为恶性.结论 Bosniak分级在肾囊性病变的MSCT诊断具有较高的应用价值,有助于肾囊性病变的诊断和鉴别诊断以及临床治疗方案的决策.     

Cystic abdominal masses in children: a pictorial essay

Cystic abdominal masses in children are not an infrequently encountered condition of childhood. These lesions usually present with large size and mimick each other with similar presenting symptoms. Imaging examinations have an important role to determine the type of the cystic abdominal masses, which is crucial for management of patients and presurgical planning. In this pictorial essay, we summarized the imaging features of common cystic abdominal masses of children, including cystic lesions arising from liver, biliary ducts, kidney, pancreas, bowel, ovary, mesentery, and miscellaneous tissues.