FDG-PET/CT detected occult metastatic disease in seven of 42 patients with negative conventional preoperative evaluations. PET findings were strongly correlated with survival. As such, FDG-PET/CT may help in making treatment decisions before radical cystectomy.

Renal cell carcinoma (RCC) is the most common malignant tumor involving the kidney. Determining the subtypes of renal cell carcinoma is among the major goals of preoperative radiological work-up. Among all modalities, magnetic resonance imaging (MRI) has several advantages, such as inherent soft tissue contrast, detection of lipid and blood products, and excellent sensitivity to detect small amounts of intravenous contrast, which facilitate the discrimination of subtypes of RCC. In this article, we review MRI and pathological features used for determining the main histologic subtypes of RCC, including clear cell, papillary, collecting duct, chromophobe, multilocular cystic, and unclassified RCC. Renal cell carcinoma (RCC) is the most common malignant epithelial tumor of the kidney, accounting for 85%-90% of all solid renal tumors in adults and comprising 1%-3% of all malignant visceral neoplasms (1). Approximately 40% of patients with RCC eventually die from progression of this disease, making it the most lethal urologic malignancy (2). Today, most RCC instances are incidental masses identified on imaging studies performed for nonurological reasons.Percutaneous biopsy is a minimally invasive method, and its accuracy for identifying renal tumors ranges from 70% to 90% (3, 4). However, widespread use of percutaneous biopsy remains controversial due to the potential complications of biopsy, the possibility of sampling errors, the dependence on an adequate biopsy sample for analysis, and concerns about how the biopsy information might alter the treatment plan (5). Therefore, histopathological characterization of renal masses with magnetic resonance imaging (MRI) compared with percutaneous biopsy becomes more advantageous.Determining subtypes of RCC has significant prognostic and theraupeutic implications for patients who are poor surgical candidates, for patients who have a metastatic disease, for surgical planning in patients who are surgical candidates, and for immunotherapy and use of the tyrosine kinase inhibitors "sunitinib" and "sorafenib" for clear cell RCC and "temsirolimus" for papillary RCC (6-9).The need for a different approach to the management of RCC among classical surgical procedures has arisen. Nephron-preserving surgical methods, cryoablation, radiofrequency ablation, targeted molecular therapy or follow-up, and MRI are believed to surpass other modalities both in the diagnosis of RCC and determination of its subtypes (10,11).In this article, we review MRI findings and pathological features used for determining the main histologic subtypes of RCC, including clear cell carcinoma, papillary, collecting duct, chromophobe, multilocular cystic, and unclassified RCC. The role of MRI in renal imagingThere are three indispensable components of renal MRI: breathhold imaging, three-dimensional (3D) gradient echo pulse sequence, and fat detection techniques.Breathhold imaging is one of the essential techniques in renal mass MRI protocols. Suspended expiration eliminates respiratory motion artifacts an...

In hyperechoic renal masses, the presence of shadowing, a hypoechoic rim, and intratumoral cysts are important findings that may help distinguish AML from RCC.

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