Differentiation of subtypes of renal cell carcinoma on helical CT scans

Subtype differentiation of small renal cell carcinomas on three-phase MDCT: usefulness of the measurement of degree and heterogeneity of enhancement

BACKGROUND

Subtype differentiation of small renal cell carcinomas (RCCs) can provide more information to surgeons and patients and get more useful information about imaging features of small renal tumors.

PURPOSE

To evaluate the usefulness of the measurement of degree and heterogeneity of enhancement in subtype differentiation of small renal cell carcinomas (RCCs) by three-phase multidetector-row CT (MDCT).

MATERIAL AND METHODS

We reviewed 149 pathologically confirmed small (<4cm) RCCs in 143 patients: 114 (clear cell), 17 (chromophobe), and 18 papillary (8 papillary type 1 and 10 papillary type 2). Scans in pre-contrast, corticomedullary, and nephrographic phases were obtained. We assessed the mean and standard deviation of the Hounsfield units (HU) in a region of interest (ROI) for the degree of enhancement and the heterogeneity of enhancement, respectively. We compared the attenuation values, and the degree and heterogeneity of enhancement among the subtypes.

RESULTS

The clear cell type showed the highest enhancement and heterogeneity of enhancement followed by chromophobe and papillary types. There was a significant difference in enhancement between the clear cell and papillary types in the corticomedullary phase (P < 0.01), and between clear and non-clear cell types in the nephrographic phase (P < 0.05). Heterogeneity of enhancement showed a significant difference between clear cell and non-clear cell types in the corticomedullary phase (P < 0.05).

CONCLUSION

The measurement of degree and heterogeneity of enhancement on contrast-enhanced MDCT may be a simple and useful method to differentiate between the different types of small RCCs.

Radiological findings of renal leiomyomas: a report of five surgically confirmed cases

BACKGROUND

To describe radiological features of renal leiomyomas.

METHODS

We retrospectively reviewed radiological findings of surgically confirmed renal leiomyomas in five patients. Three patients only underwent CT examinations, while two patients received both CT and MR examinations.

RESULTS

Six renal leiomyomas were found in the five patients, which located in the right kidney. Four tumors were at the periphery of the kidney, one tumor was in the renal parenchyma, and one tumor located in the renal pelvis. At plain CT scans, five lesions were homogeneous dense with three hyperdense and two isodense, while one lesion was heterogeneous dense. At MR imaging, one lesion was heterogeneous signal and two lesions were homogeneous signal. After i.v. contrast materials, all lesions demonstrated homogenous or heterogeneous enhancement which were lower than the renal cortex at the corticomedullary phase. A trend of continuous and homogeneous enhancement was observed in dynamic enhancement on CT and MR imaging.

CONCLUSION

Renal leiomyomas have some characteristic radiological findings, such as homogeneous density or signal peripheral mass with well-defined margins, less heterogeneous or homogeneous enhancement than adjacent renal cortex at the corticomedullary phase, a trend of continuous and homogeneous on later phase of dynamic scanning.

Evaluation of renal masses with contrast-enhanced ultrasound: initial experience

OBJECTIVE

Nearly 25% of solid renal tumors are indolent cancer or benign and can be managed conservatively in selected patients. This prospective study was performed to determine whether preoperative IV microbubble contrast-enhanced ultrasound can be used to differentiate indolent and benign renal tumors from more aggressive clear cell carcinoma.

SUBJECTS AND METHODS

Thirty-four patients with renal tumors underwent preoperative gray-scale, color, power Doppler, and octafluoropropane microbubble IV contrast-enhanced ultrasound. Three blinded radiologists reading in consensus compared rate of contrast wash-in, grade and pattern of enhancement, and contrast washout compared with adjacent parenchyma. Contrast ultrasound findings were compared with surgical histopathologic findings for all patients.

RESULTS

The 34 patients had 23 clear cell carcinomas, three type 1 papillary carcinomas, one chromophobe carcinoma, one clear rare multilocular low-grade malignant tumor, two unclassified lesions, three oncocytomas, and one benign angiomyolipoma. The combination of heterogeneous lesion echotexture and delayed lesion washout had 85% positive predictive value, 43% negative predictive value, 48% sensitivity, and 82% specificity for predicting whether a lesion was conventional clear cell carcinoma or another tumor. Diminished lesion enhancement grade had 75% positive predictive value, 81% negative predictive value, 55% sensitivity, and 91% specificity for non-clear cell histologic features, either benign or low-grade malignant. Combining delayed washout with quantitative lesion peak intensity of at least 20% of kidney peak intensity had 91% positive predictive value, 40% negative predictive value, 63% sensitivity, and 80% specificity in the prediction of clear cell histologic features.

CONCLUSION

Ultrasound features of gray-scale heterogeneity, lesion washout, grade of contrast enhancement, and quantitative measure of peak intensity may be useful for differentiating clear cell carcinoma and non-clear cell renal tumors.

Comparison and assessment of semi-automatic image segmentation in computed tomography scans for image-guided kidney surgery

PURPOSE

Image segmentation is integral to implementing intraoperative guidance for kidney tumor resection. Results seen in computed tomography (CT) data are affected by target organ physiology as well as by the segmentation algorithm used. This work studies variables involved in using level set methods found in the Insight Toolkit to segment kidneys from CT scans and applies the results to an image guidance setting.

METHODS

A composite algorithm drawing on the strengths of multiple level set approaches was built using the Insight Toolkit. This algorithm requires image contrast state and seed points to be identified as input, and functions independently thereafter, selecting and altering method and variable choice as needed.

RESULTS

Semi-automatic results were compared to expert hand segmentation results directly and by the use of the resultant surfaces for registration of intraoperative data. Direct comparison using the Dice metric showed average agreement of 0.93 between semi-automatic and hand segmentation results. Use of the segmented surfaces in closest point registration of intraoperative laser range scan data yielded average closest point distances of approximately 1 mm. Application of both inverse registration transforms from the previous step to all hand segmented image space points revealed that the distance variability introduced by registering to the semi-automatically segmented surface versus the hand segmented surface was typically less than 3 mm both near the tumor target and at distal points, including subsurface points.

CONCLUSIONS

Use of the algorithm shortened user interaction time and provided results which were comparable to the gold standard of hand segmentation. Further, the use of the algorithm's resultant surfaces in image registration provided comparable transformations to surfaces produced by hand segmentation. These data support the applicability and utility of such an algorithm as part of an image guidance workflow.

Clear cell renal cell carcinoma: multiphasic multidetector CT imaging features help predict genetic karyotypes

PURPOSE

To determine whether imaging characteristics at multiphasic multidetector computed tomography (CT) correlate with common karyotypic abnormalities in patients with clear cell renal cell carcinomas (ccRCCs).

MATERIALS AND METHODS

Institutional review board approval was obtained, and informed consent was waived for this HIPAA-compliant retrospective study. From January 2000 through September 2007, the prenephrectomy multiphasic (corticomedullary, nephrographic, and excretory phases), multidetector helical CT images of 58 histologically proved and karyotyped ccRCCs were reviewed by two readers with experience in abdominal imaging. Imaging features assessed included degree of attenuation, contour, and presence of calcifications and neovascularity. These features were independently correlated with specific karyotypic abnormalities on the resected specimens. Degree of attenuation data were analyzed with logistic regression for significance (P < .05), and morphologic characteristics were analyzed with odds ratios for assessing their diagnostic power.

RESULTS

On unenhanced scans, 7% (two of 28) of ccRCCs with the loss of chromosome 3p were calcified, whereas 37% (11 of 30) of lesions without this anomaly were calcified (odds ratio, 0.13). During the corticomedullary phase, ccRCCs with the loss of chromosome Y enhanced more than those without this anomaly (130.0 vs 102.5 HU, P = .04), and ccRCCs with trisomy 7 enhanced less than those without this anomaly (105.8 vs 139.3 HU, P = .04). During the excretory phase, ccRCCs with trisomy 5 enhanced more than those without this anomaly (115.5 vs 83.4 HU, P = .03).

CONCLUSION

The genetic makeup of ccRCCs affects their imaging features at multidetector CT examinations. Multidetector CT imaging characteristics may help suggest differences at the cytogenetic level among ccRCCs.

[MDCT patterns of presentation of pancreatic metastases from renal cell carcinoma]

OBJECTIVE

To determine the frequency of pancreatic metastasis from renal cell carcinoma in patients studied with MDCT during 2007 and to describe the patterns of presentation on MDCT.

MATERIAL AND METHODS

We retrospectively studied 133 patients with renal cell carcinoma who underwent MDCT between January and December 2007. Forty-nine patients presented disseminated disease. We analyzed the frequency, location, and patterns of presentation of pancreatic metastases.

RESULTS

Pancreatic involvement was identified in six patients. Four patients had isolated pancreatic nodules and two presented multiple nodules. A total of nine pancreatic lesions ranging between 8mm and 40 mm were detected. All nodules had increased uptake of contrast material in the arterial phase except for one in a patient with multiple nodules, due to necrosis. Two cases were associated with pancreatic duct dilation. Histology was obtained in only one patient.

CONCLUSION

Pancreatic involvement of renal cell carcinoma was detected in 4.5% of patients, ranking fifth in frequency in patients with disseminated disease. The arterial phase is necessary to detect pancreatic involvement of renal cell carcinoma. The pattern of presentation is nearly constant, helping differentiate pancreatic metastasis from primary pancreatic adenocarcinoma.

Imaging of renal cell carcinoma: state of the art and recent advances

BACKGROUND AND AIM

Renal cell carcinoma (RCC) is the 13th most common cancer worldwide and accounts for 4% of all adult malignancies. Herein the state of the art and recent advances in cross-sectional radiological imaging applied to RCC are reviewed, including ultrasonography, computed tomography, magnetic resonance imaging, and positron emission tomography.

METHODS

Literature search of peer-reviewed papers published by October 2010.

RESULTS

In front of more conventional and widespread imaging tools, such as ultrasonography and computed tomography, an array of newer and attractive radiological modalities are under investigation and show promise to improve our ability to noninvasively detect renal tumors and its recurrences, accurately assess the extent of the disease, and reliably evaluate treatment response, particularly in the era of antiangiogenetic therapy.

CONCLUSIONS

Recent major advances in radiological imaging techniques have considerably improved our ability to diagnose, stage and follow-up RCC. Further studies are needed to evaluate the potential of most recent and still investigational imaging tools.

Differentiation of oncocytoma and renal cell carcinoma in small renal masses (<4 cm): the role of 4-phase computerized tomography

PURPOSE

We investigate the use of 4-phase computerized tomography with intravenous contrast to help distinguish oncocytoma from renal cell carcinoma (RCC) in tumors <4 cm.

METHODS

We retrospectively identified patients who underwent surgical management for renal tumors <4 cm from 2005 to 2008. Patients who had pre-operative CT evaluation as per our institution's renal mass protocol and had confirmed pathological diagnosis of either oncocytoma or RCC were included in the study. Enhancement readings were obtained for the tumor and the renal cortex using the same slice simultaneously.

RESULTS

Our cohort involved 69 patients (46 men, 23 women; mean age 66) who presented with 79 renal masses. Histopathologically 40 were clear cell, 22 papillary, 5 chromophobe RCC and 12 oncocytoma. On the arterial, venous and delayed phase images, oncocytoma showed the highest mean enhancement change, i.e.,546, 396 and 239% followed by clear cell RCC 261, 261 and 174%, chromophobe RCC 147, 127 and 66% and papillary RCC 137, 184 and 118%, respectively. The enhancement pattern differed significantly on comparing oncocytoma with RCC (P < 0.007). The mean percentage contrast excreted at the end of the delayed phase was 33.3, 13.8, 32 and 53% for clear cell, papillary, chromophobe and oncocytoma, respectively.

CONCLUSION

The enhancement and washout values in Hounsfield units obtained by multiphasic CT scan aid in distinguishing oncocytoma from the commonly seen subtypes of RCC in renal masses <4 cm. This preliminary study demonstrates that arterial phase enhancement greater than 500% and washout values of greater than 50% are exclusively seen in renal oncocytomas.

Midterm results of radiofrequency ablation versus nephrectomy for T1a renal cell carcinoma

PURPOSE

The aim of this study was to retrospectively evaluate midterm results of renal radiofrequency (RF) ablation compared to the results after nephrectomy in patients with T1a renal cell carcinoma (RCC).

MATERIALS AND METHODS

A total of 115 patients with a single RCC measuring </=4 cm (T1a) were included; 51 patients underwent RF ablation, 54 patients radical nephrectomy, and 10 patients partial nephrectomy. The survival and the percent decreases in glomerular filtration rate (GFR) were compared among the three treatments.

RESULTS

Although overall survival after RF ablation (75.0% at 5 years) was lower than those after radical and partial nephrectomy, the RCC-related survival (100% at 5 years) was comparable to those following radical nephrectomy (100% at 5 years) and partial nephrectomy (100% at 3 years). The disease-free survival (DFS) after RF ablation (98.0% at 5 years) was also comparable to those after radical nephrectomy (95.0% at 5 years) (P = 0.72) and partial nephrectomy (75.0% at 3 years) (P = 0.13). The percent decrease in the GFR at last follow-up in the RF ablation group (median 7.9%) was significantly lower than that in the radical nephrectomy group (median 29.0%) (P < 0.001) and comparable to that in the partial nephrectomy group (median 11.5%) (P = 0.73).

CONCLUSION

RF ablation provides RCC-related and DFS comparable to that found after nephrectomy with little loss of renal function.

How not to miss or mischaracterize a renal cell carcinoma: protocols, pearls, and pitfalls

OBJECTIVE

MDCT protocol optimization for renal cell carcinoma requires attention to several data acquisition, reconstruction, and display parameters. Specifically, multiple acquisitions with varying coverage, careful timing of each contrast-enhanced phase, and use of 2D and 3D multiplanar displays are required. This article reviews these parameters, supplemented by experience-based pearls and pitfalls.

CONCLUSION

Proper data acquisition and utilization of postprocessing tools are essential to avoid missed diagnoses or misinterpretation when imaging renal cell carcinoma.

Exophytic renal masses: angular interface with renal parenchyma for distinguishing benign from malignant lesions at MR imaging

PURPOSE

To retrospectively determine whether benign exophytic renal masses can be distinguished from renal cell carcinoma (RCC) on the basis of angular interface at single-shot fast spin-echo (SE) T2-weighted magnetic resonance (MR) imaging.

MATERIALS AND METHODS

This retrospective study was compliant with HIPAA and was approved by the institutional review board. Patient informed consent was waived. A total of 162 exophytic (2 cm or greater) renal masses in 152 patients (103 men, 49 women; mean age, 58 years; age range, 23-85 years) were included. Two radiologists independently recorded the mass size and angular interface on single-shot fast SE T2-weighted MR images. Surgical pathologic report and MR follow-up were used as reference standards. Logistic regression analysis was used to examine the usefulness of these variables for differentiating benign masses from RCCs. Diagnostic performance was analyzed by comparing values for area under receiver operating characteristic curve (A(z)). Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of angular interface for diagnosing benign masses were calculated. Reader agreement was assessed with kappa-weighted statistics and intraclass correlation coefficients (ICCs).

RESULTS

Of 162 masses, 65 were benign, and 97 were RCCs. The sensitivity, specificity, PPV, NPV, and A(z) of angular interface for diagnosing benign masses were 78%, 100%, 100%, 87%, and 0.813, respectively. Angular interface (P < .001) was a significant predictor of benign renal mass but mass size (P = .66) was not. There was almost perfect interobserver agreement for mass size (ICC = 0.96) and angular interface (kappa = 0.91).

CONCLUSION

The presence of an angular interface with the renal parenchyma at single-shot fast SE T2-weighted MR imaging is a strong predictor of benignity in an exophytic renal mass 2 cm or greater in diameter with high specificity and diagnostic accuracy.

Imaging angiogenesis of genitourinary tumors

Angiogenesis is a key process in the growth and metastasis of cancer, and genitourinary tumors are no exception. The evolution of angiogenesis as an important target for novel anticancer therapeutics has brought with it new challenges for in vivo imaging. Most imaging techniques quantify physiological parameters, such as blood volume and capillary endothelial permeability. Although CT, PET and ultrasonography have shown promise, MRI is the most common method used to evaluate angiogenesis in clinical trials of genitourinary tumors. Pilot studies of MRI, CT and ultrasonography in patients with renal cancer have produced promising results; reductions in vascular permeability and blood flow have been correlated with progression-free survival. The vascular characteristics of prostate cancer have been evaluated by MRI, and this has been suggested as a means of assessing tumor response to hormone deprivation therapy. Current evidence highlights the potential of angiogenesis imaging in the diagnosis, staging and possibly response monitoring of bladder cancer. In the future, assessment of the angiogenic process at the structural, functional and molecular levels, before, during and after antiangiogenic therapy will undoubtedly be integrated into wider clinical practice.

[Clinical factors associated with benign renal tumors]

OBJECTIVES

In this study, we sought to define the incidence of benign renal tumors in our institute and to clarify the clinical factors associated with benign renal tumors, in order to assist in forming preoperative differential diagnoses.

METHODS

From October 2002 to July 2007, we performed 157 nephrectomies in patients preoperatively diagnosed with renal cell carcinoma. We chose 81 tumors, all of which were less than 5 cm, for further study. We reviewed double-phase helical CT imaging retrospectively, specifically focusing on attenuation patterns and homogeneity. We also compared clinical factors, including age, sex and tumor size, between the benign and malignant renal tumors.

RESULTS

The patient's median age was 67 years (mean age, 63 years), and the median tumor diameter was 3.0 cm (mean, 3.2 cm). Benign renal tumors were found in 10 (12%) of the 81 tumors; these included seven cases of oncocytoma and three cases of angiomyolipoma with minimal fat. Several factors were significant clinical determinants of differentiation between benign and malignant renal tumors: homogeneity in CT, female gender, and small tumor size all predominated in cases of benign tumors. Attenuation pattern in CT, however, was not a significant factor (p = 0.344).

CONCLUSIONS

When a patient, especially a female, presents with a small and homogeneous renal tumor, careful consideration should be given to the possibility of a benign process, which needs further consideration before performing excessive surgery.

Papillary renal cell carcinoma: radiologic-pathologic correlation and spectrum of disease

Papillary renal cell carcinoma (pRCC) is the second most common type of renal cell carcinoma (RCC). pRCC has unique imaging and clinical features that may allow differentiation from clear cell RCC (cRCC). There have been significant advances in our knowledge of the natural history and treatment of pRCC, with data suggesting that it may be best to manage pRCC differently from the other subtypes of RCC. At contrast material-enhanced computed tomography, pRCC enhances less than does cRCC in all phases of contrast-enhanced imaging. The difference in the degree of enhancement between pRCC and cRCC is due to differences in their intratumoral vascularity. In general, if a heterogeneous mass enhances to a degree similar to that manifested by the renal cortex, it is likely to be a cRCC. A mass that enhances to a lesser degree is likely to be a non-clear cell RCC. It is common for metastatic lesions from pRCC to show enhancement characteristics similar to those of the primary tumor and be hypovascular.

Renal cell carcinoma: t1 and t2 signal intensity characteristics of papillary and clear cell types correlated with pathology

OBJECTIVE

The objective of our study was to describe the T1 and T2 signal intensity characteristics of papillary renal cell carcinoma (RCC) and clear cell RCC with pathologic correlation.

MATERIALS AND METHODS

Of 539 RCCs, 49 tumors (21 papillary RCCs and 28 clear cell RCCs) in 45 patients were examined with MRI. Two radiologists retrospectively and independently assessed each tumor's T1 and T2 signal intensity qualitatively and quantitatively (i.e., the signal intensity [SI] ratio [tumor SI / renal cortex SI]). Of the 49 tumors, 37 (76%) were assessed for pathology features including tumor architecture and the presence of hemosiderin, ferritin, necrosis, and fibrosis. MRI findings and pathology features were correlated. Statistical methods included summary statistics and Wilcoxon's rank sum test for signal intensity, contingency tables for assessing reader agreement, concordance rate between the two readers with 95% CIs, and Fisher's exact test for independence, all stratified by RCC type.

RESULTS

Papillary RCCs and clear cell RCCs had a similar appearance and signal intensity ratio on T1-weighted images. On T2-weighted images, most papillary RCCs were hypointense (reader 1, 13/21; reader 2, 14/21), with an average mean signal intensity ratio for both readers of 0.67 +/- 0.2, and none was hyperintense, whereas most clear cell RCCs were hyperintense (reader 1, 21/28; reader 2, 17/28), with an average mean signal intensity ratio for both readers of 1.41 +/- 0.4 (p < 0.05). A tumor T2 signal intensity ratio of < or = 0.66 had a specificity of 100% and sensitivity of 54% for papillary RCC. Most T2 hypointense tumors exhibited predominant papillary architecture; most T2 hyperintense tumors had a predominant nested architecture (p < 0.05).

CONCLUSION

On T2-weighted images, most papillary RCCs are hypointense and clear cell RCCs, hyperintense. The T2 hypointense appearance of papillary RCCs correlated with a predominant papillary architecture at pathology.

Segmental enhancement inversion at biphasic multidetector CT: characteristic finding of small renal oncocytoma

PURPOSE

To retrospectively determine the usefulness of segmental enhancement inversion during the corticomedullary phase (CMP) and early excretory phase (EEP) of biphasic multidetector computed tomography (CT) in differentiating small renal oncocytoma from renal cell carcinoma (RCC).

MATERIALS AND METHODS

This retrospective study was institutional review board approved; informed consent was waived. Between January 2004 and December 2006, 98 patients with pathologically confirmed renal masses smaller than 4 cm (10 renal oncocytomas and 88 RCCs) were included in this study. Segmental enhancement inversion was defined as follows: In a mass with two segments showing different degrees of enhancement during CMP, the relatively highly enhanced segment became less enhanced during EEP, whereas the less-enhanced segment during CMP became highly enhanced during EEP. Two experienced radiologists retrospectively assessed the presence of segmental inversion in all masses and measured attenuation with consensus. The Fisher exact test was used to determine the significance of segmental enhancement inversion in differentiating small renal oncocytoma from RCC.

RESULTS

Eight of 10 renal oncocytomas and only one of 88 RCCs showed segmental inversion during CMP and EEP, which significantly differentiated small renal oncocytomas and RCCs (P < .0001). For differentiating oncocytoma from RCC, segmental inversion was found to have a sensitivity of 80% (eight of 10), a specificity of 99% (87 of 88), a positive predictive value of 89% (eight of nine), and a negative predictive value of 98% (87 of 89). The mean values of the attenuation differences shown by two segments during CMP and EEP were 62.75 HU +/- 36.96 (standard deviation) and -36.88 HU +/- 20.02, respectively.

CONCLUSION

Segmental enhancement inversion during CMP and EEP was found to be a characteristic enhancement pattern of small renal oncocytoma at biphasic multidetector CT and it may help in differentiating small oncocytoma from RCC.

SUPPLEMENTAL MATERIAL

http://radiology.rsnajnls.org/cgi/content/full/2522081180/DC1.

Differential diagnosis of complex cystic renal mass using multiphase computerized tomography

PURPOSE

We evaluated the additional usefulness of multiphase computerized tomography for improving the differential diagnosis of cystic renal masses by the Bosniak classification.

MATERIALS AND METHODS

We reviewed the records of 104 patients with Bosniak class II (29 or 27.8%), III (38 or 36.5%) and IV (37 or 35.7%) cystic renal masses managed surgically between 1997 and 2007. On preoperative multiphase computerized tomography enhancement differences in HU between the precontrast and corticomedullary phases were measured at the highest enhancement area to correlate with pathological findings.

RESULTS

Renal cell carcinoma was diagnosed in 56 patients (53.8%). Of the tumors 35 (62.5%) showed clear cell histology. According to Bosniak class 3 (11.5%), 21 (55.2%) and 32 (86.4%) class II to IV lesions, respectively, were diagnosed as renal cell carcinoma. For renal cell carcinoma and benign cysts mean HU at the precontrast phase was similar (31.5 and 32.4 HU, respectively), while renal cell carcinoma showed a significantly higher measurement at the corticomedullary phase (112.9 vs 59.8 HU, p <0.0001). To differentiate renal cell carcinoma a corticomedullary phase minus precontrast phase value of greater than 42 HU was predictive with 97.1% sensitivity and 85.7% specificity (area under the ROC curve 0.966). In a multiple regression model the corticomedullary phase minus precontrast phase value and the Bosniak classification independently determined malignant pathological findings (corticomedullary phase minus precontrast phase greater than 42 HU HR 31.541, 95% CI 8.320-119.563 and Bosniak class HR 5.545, 95% CI 2.153-14.279, each p <0.0001).

CONCLUSIONS

In cases of complex cystic renal masses diagnostic accuracy can be improved to differentiate renal cell carcinoma by combining Bosniak class and enhancement differences measured on multiphase computerized tomography between precontrast and maximal enhancement phases. This would help determine the need for and the method of surgical treatment.

Renal cell carcinoma: dynamic contrast-enhanced MR imaging for differentiation of tumor subtypes--correlation with pathologic findings

PURPOSE

To retrospectively evaluate whether the enhancement patterns of pathologically proved clear cell, papillary, and chromophobe renal cell carcinomas (RCCs) measured on clinical dynamic contrast agent-enhanced magnetic resonance (MR) images permit accurate diagnosis of RCC subtype.

MATERIALS AND METHODS

This study was Institutional Review Board approved and HIPAA compliant; informed consent was waived. One hundred twelve patients (76 men, 36 women; age range, 25-88 years; mean age, 58.1 years) underwent MR imaging of 113 renal masses (mean diameter, 5.4 cm) with pathologic diagnoses of clear cell (n = 75), papillary (n = 28), or chromophobe (n = 10) RCC. A 1.5-T clinical MR protocol was used before and after (corticomedullary and nephrographic phases) intravenous administration of contrast agent. Region-of-interest measurements within tumor and uninvolved renal cortex were used to calculate percentage signal intensity change and tumor-to-cortex enhancement index. Subtype groups were compared by using linear mixed-effects models. Receiver operating characteristic (ROC) curve analysis was performed for the comparison of clear cell and papillary RCCs.

RESULTS

On both the corticomedullary and nephrographic phase images, clear cell RCCs showed greater signal intensity change (205.6% and 247.1%, respectively) than did papillary RCCs (32.1% and 96.6%, respectively) (P < .001). Chromophobe RCCs showed intermediate change (109.9% and 192.5%, respectively). The tumor-to-cortex enhancement indexes at corticomedullary and nephrographic phases were largest for clear cell RCCs (1.4 and 1.2, respectively), smallest for papillary RCCs (0.2 and 0.4, respectively), and intermediate for chromophobe RCCs (0.6 and 0.8, respectively). Signal intensity changes on corticomedullary phase images were the most effective parameter for distinguishing clear cell and papillary RCC (area under ROC curve, 0.99); a threshold value of 84% permitted distinction with 93% sensitivity and 96% specificity.

CONCLUSION

Clear cell, papillary, and chromophobe RCCs demonstrate different patterns of enhancement on two-time point clinical dynamic contrast-enhanced MR images, allowing their differentiation with high sensitivity and specificity.

Radiologic evaluation of small renal masses (I): pretreatment management

When characterizing a small renal mass (SRM), the main question to be answered is whether the mass represents a surgical or nonsurgical lesion or, in some cases, if followup studies are a reasonable option. Is this a task for a urologist or a radiologist? It is obvious that in the increasing clinical scenario where this decision has to be made, both specialists ought to work together. This paper will focus on the principles, indications, and limitations of ultrasound, CT, and MRI to characterize an SRM in 2008 with a detailed review of relevant literature. Special emphasis has been placed on aspects regarding the bidirectional information between radiologists and urologists needed to achieve the best radiological approach to an SRM.

Renal-adrenal fusion: instance of an adrenal adenoma mimicking a solid renal mass at CT--case report

The authors report an unusual case of unilateral renal-adrenal fusion with a concurrent adrenal adenoma. At computed tomography, this abnormality appeared as a solid enhancing lesion in the upper pole of the kidney, mimicking a renal mass. The ambiguous characteristics of this lesion at cross-sectional imaging, along with alternative diagnostic possibilities, are discussed.

Distribution of renal tumor growth rates determined by using serial volumetric CT measurements

PURPOSE

To retrospectively determine the distribution of growth rates across different sizes and subtypes of renal cortical tumors by assessing tumor volume and maximum tumor diameter at serial volumetric computed tomographic (CT) examinations.

MATERIALS AND METHODS

The institutional review board approved this retrospective, HIPAA-compliant study. Fifty-three of 2304 patients (34 men, 19 women; mean age, 67 years +/- 10 [standard deviation; range, 39-88 years) who underwent nephrectomy from 1989 to 2006 did not receive preoperative chemotherapy or radiation therapy and underwent at least two preoperative contrast material-enhanced CT examinations (at least 3 months apart) with identical section thickness that was no more than one-fifth of longitudinal tumor diameter. Tumor volume and maximum diameter were measured on CT scans. Reciprocal of doubling time (DT) (RDT) was calculated. Analysis of variance and Student t tests were performed.

RESULTS

Thirty-two clear cell carcinomas, 10 papillary carcinomas, six chromophobe carcinomas, four oncocytomas, and one angiomyolipoma were analyzed. Median tumor size was 2.9 cm (range, 1-12 cm). Seven tumors did not increase in volume. DT ranged from -78476.54 to 18057.43 days (mean, -1230.73 days; median, 590.51 days). [corrected] Growth rate determined by using maximum diameter ranged from -10.8 to 33.2 mm/y (mean, 5.1 mm/y; median, 3.5 mm/y). Faster-growing tumors were more likely to be clear cell carcinomas, those of higher grade had higher growth rates. No significant correlation was found between RDT and tumor initial volume, subtype, or grade. Small renal tumors (<or=3.5 cm) were similar to larger tumors in subtype and growth rate. Age at diagnosis correlated negatively with renal tumor growth rate (P = .03).

CONCLUSION

Growth rates in renal tumors of different sizes, subtypes, and grades represent a wide range and overlap substantially. Small renal tumors appear to be similar to larger ones in nature.

Differentiation of pathologic subtypes of papillary renal cell carcinoma on CT

OBJECTIVE

We reviewed the CT findings of the subtypes of papillary renal cell carcinoma (RCC), which behave differently clinicopathologically.

CONCLUSION

The CT features of the two pathologic subtypes of papillary RCC differ, probably reflecting their different pathologic features. Type 1 tumors have more distinct margins than type 2 tumors and have homogeneous density. Although type 2 tumors in the early stages show findings similar to those of type 1 tumors, they are at more advanced stages on the whole, with CT features showing indistinct margins, frequent centripetal infiltration, and tumor thrombi in all pT3b cases. Radiologists should be familiar with the CT features of papillary RCC that suggest different pathologic behaviors, such as tumor stage, tumor proliferation, and microvascular or vascular invasion.

Chromophobe renal cell carcinoma with calcification: Report of a case with rare finding on aspiration smears

Chromophobe renal cell carcinoma (ChRCC) is a distinct variant of renal cell carcinoma. It is important to identify this entity because it has a significantly better prognosis than clear cell (conventional) renal cell carcinoma. We report the case of a 56-year-old male who presented with 10 days history of painless hematuria. There was no palpable swelling or systemic symptoms. On radiological examination the possibility of a right renal neoplasm was considered. Ultrasound guided aspiration was done and cytological features of ChRCC were noted. In addition, numerous foci of calcification were seen, which was an unusual cytological feature for ChRCC. The characteristic cytomorphology of ChRCC makes it possible to render a preoperative diagnosis on fine needle aspiration cytology (FNAC). We report the case to emphasize the importance and possibility of diagnosing of ChRCC on cytology. In addition, the extensive calcification as seen in our case is an unusual cytological finding not previously reported in cytology smears.

Renal cell carcinoma: diagnosis, staging, and surveillance

OBJECTIVE

This educational review focuses on the staging and radiologic evaluation of renal cell carcinoma. It includes discussion of the epidemiology, pathology, and therapeutic options of renal cell carcinoma and the implications for radiologic follow-up.

CONCLUSION

The incidence of renal cell carcinoma has been increasing. Imaging plays a central role in its detection, staging, and treatment evaluation and follow-up.