THE KIDNEY

Evaluating hemorrhage in renal cell carcinoma using susceptibility weighted imaging

Background

Intratumoral hemorrhage is a frequent occurrence in renal cell carcinoma and is an indicator of tumor subtype. We hypothesize that susceptibility weighted imaging (SWI) is sensitive to hemorrhage in renal cell carcinoma and can give a more diagnostic image when compared to conventional imaging techniques.

Materials and Methods

A retrospective review of 32 patients with clear cell renal cell carcinoma was evaluated. All patients underwent magnetic resonance imaging (MRI) and 22 out of 32 patients also underwent a computed tomography (CT) scan. Hemorrhage was classified into 3 different categories according to shape and distribution. Histopathology was obtained from all masses by radical nephrectomy. The ability to detect the presence of hemorrhage using CT, non-contrast conventional MRI and SWI was evaluated, and the patterns of hemorrhage were compared.

Results

Using pathologic results as the gold standard, the sensitivities of non-contrast conventional MRI, SWI and CT in detecting hemorrhage in clear cell renal cell carcinoma were 65.6%, 100% and 22.7%, respectively. Accuracy of non-contrast conventional MRI and SWI in evaluating hemorrhagic patterns were 31.3% and 100%, respectively.

Conclusion

These results demonstrate that SWI can better reveal hemorrhage and characterize the pattern more accurately than either non-contrast conventional MRI or CT. This suggests that SWI is the technique of choice for detecting hemorrhagic lesions in patients with renal cancer.

Assessment and characterisation of common renal masses with CT and MRI

Objective

Owing to the widespread use of abdominal imaging studies the detection rate of solid renal masses has increased, and an accurate characterisation of imaging features of renal masses has become more essential for case management.

Method and results

MR imaging (MRI) and computed tomography (CT) are frequently used modalities for detection and differentiation of renal masses. This article gives a review of imaging characteristics of benign and malignant renal masses, discussing their appearance in CT and MR imaging. Advanced MR techniques like diffusion-weighted imaging and apparent diffusion coefficient (ADC) mapping, which have shown promising results in the differentiation between benign and malignant renal lesions, will be introduced.

Conclusion

MRI and CT are useful in the characterisation and estimation of the prognosis for renal masses.

Significance of the pseudocapsule on MRI of renal neoplasms and its potential application for local staging: a retrospective study

OBJECTIVE

The purpose of our study was to evaluate the role of MRI in showing a pseudocapsule for local staging of renal tumors, and its potential application to select patients for partial surgery.

MATERIALS AND METHODS

Eighty tumors (73 renal cell carcinomas [RCCs] and seven oncocytomas) were preoperatively evaluated by MRI. MRI findings were assessed with a special focus on perinephric fat and pseudocapsule. Correlations were performed with pathologic staging after surgery.

RESULTS

At pathology, a pseudocapsule was recognized in 79 cases. Twenty-three RCC were staged pT3a (21 clear cell; two papillary). MR images exhibited a pseudocapsule in 90% of cases as a hypointense rim surrounding the tumor on T2-weighted images. MRI findings concerning isolated analysis of the pseudocapsule for differentiating stage T1/T2 from T3a were sensitivity: 86%, 50%; specificity: 95%, 92%; positive predictive value: 95%, 33%; negative predictive value: 88%, 92%; and accuracy: 93%, 89%, for clear cell and papillary types, respectively. For stage T3a, with both abnormalities of the pseudocapsule and perirenal fat, results were, for overall RCC sensitivity: 84%; specificity: 95%; positive predictive value: 91%; negative predictive value: 91%; and accuracy: 91%.

CONCLUSION

The identification of the pseudocapsule offers an additional value for local staging by MRI. The presence of an intact pseudocapsule is a sign of lack of perinephric fat invasion. It is more likely to predict that the tumor can be removed by partial surgery.

Fine-needle aspiration of renal angiomyolipoma: Cytological findings and diagnostic pitfalls in a series of five cases

Diagnosis of renal angiomyolipoma (AML) by fine-needle aspiration (FNA) may be difficult because cytological and radiological findings sometimes overlap with renal cell carcinoma (RCC) and liposarcoma. Five FNAs of AMLs were studied. Epithelioid and spindle stromal cells were arranged in loosely cohesive clusters and singly. The chromatin was evenly distributed and bland. Occasionally nuclear atypia was identified. Nuclei were oval to elongated, nucleoli were inconspicuous or absent, naked nuclei were present in three specimens, and intranuclear inclusions were present in two specimens. The cytoplasm was delicate and sometimes finely vacuolated. Adipose tissue was observed in two specimens. Thick-walled vessels, mitoses, and necrosis were absent. Corresponding surgical material showed typical features of AML. In FNA, bland chromatin and inconspicuous nucleoli distinguish renal AML from RCC and liposarcoma. Adipose tissue is not universally present. Cellular atypia in conjunction with overlapping radiological findings with RCC and liposarcoma are potential diagnostic pitfalls. Immunocytochemical (ICC) stains may elucidate the correct diagnosis.

Renal neoplasms amenable to partial nephrectomy: MR imaging

PURPOSE

To determine the magnetic resonance (MR) imaging characteristics of renal lesions in patients who undergo technically successful partial nephrectomy.

MATERIALS AND METHODS

Between February 1991 and September 1997, 38 patients (41 lesions) who underwent partial nephrectomy at a single institution were preoperatively evaluated with contrast material-enhanced, multiplanar, surface-coil MR imaging. Imaging findings that could affect the decision to perform partial nephrectomy were retrospectively evaluated: tumor size; tumor location; presence of pseudocapsule; suspected tumor invasion of renal sinus fat, renal collecting system, renal vein, or perinephric fat; and morphologic and physiologic status of the contralateral kidney. Correlation was made with surgical and pathologic findings.

RESULTS

Thirty-three of 41 lesions (80%) were renal cell carcinomas, five were oncocytic neoplasms (12%), two were hemorrhagic cysts (5%), and one was an angiomyolipoma (2%). Twenty-four of 41 (59%) lesions had pseudocapsules. In most cases, the perinephric fat (n = 38 [93%]), the renal sinus fat (n = 31 [76%]), and the renal collecting system (n = 39 [95%]) were correctly interpreted as being uninvolved by tumor.

CONCLUSION

Renal neoplasms amenable to partial nephrectomy can be identified and characterized with contrast-enhanced, multiplanar, surface-coil MR imaging.