RESEARCH Open Access Tumor grade of clear cell renal cell carcinoma assessed by contrast-enhanced computed tomography Kousei Ishigami 1* , Leandro V Leite 1 , Marius G Pakalniskis 1 , Daniel K Lee 2 , Danniele G Holanda 3 and David M Kuehn 1 Abstract The purpose of this study was to clarify the association between CT findings and Fuhrman grade of clear cell renal cell carcinoma (ccRCC). The study group consisted of 214 surgically proven ccRCC in 214 patients. Contrast-enhanced CT studies were retrospectively assessed for tumor size, cystic versus solid, calcification, heterogeneity of lesions, percentage of non-enhancing (necrotic) areas, and growth pattern. CT findings and Fuhrman grade were compared. Nineteen of 22 (86.4%) cystic ccRCC were low grade (Fuhrman grades 1-2). There was no significant correlation between tumor size and grade in cystic ccRCC (P = 0.43). In predominantly solid ccRCC, there was significant correlation between tumor size and grade (P < 0.0001). Thirty-eight of 43 (88.4%) infiltrative ccRCC were high grade (Fuhrman grades 3-4). Logistic regression showed tumor size and infiltrative growth were significantly associated with grades 3-4 (P = 0.00083 and P = 0.0059). Cystic ccRCC tends to be low grade. Infiltrative growth and larger tumor size may increase the likelihood of high grade ccRCC. Keywords: Clear cell renal cell carcinoma; Computed tomography; Fuhrman grade; Cystic renal cell carcinoma; Growth pattern Introduction Clear cell renal cell carcinoma (ccRCC) is the most common subtype of RCC, accounting for approximately 70 - 80% of RCC (Leibovich et al. 2010; Teloken et al. 2009; Kim et al. 2002). It has a poorer prognosis than other subtypes of RCC, such as papillary and chromo- phobe RCC (Leibovich et al. 2010; Teloken et al. 2009), and its biological aggressiveness significantly affects prognosis. The system most widely employed to classify RCC is the Fuhrman grading system, which uses the characteristics of the nuclei and nucleoli of tumor cells as its basis for grad- ing (Fuhrman et al. 1982; Novara et al. 2007; Ficarra et al. 2005). Fuhrman grade 1 is the least aggressive type, with grade 4 being the most aggressive (Fuhrman et al. 1982). Grades 1–2 and 3–4 are classified as low and high grades, respectively (Novara et al. 2007; Ficarra et al. 2005). Higher grade tumors have an elevated risk of postoperative recurrence (Novara et al. 2007); thus, postoperative sur- veillance for these patients should be more rigorous. The Fuhrman grade is one of the most effective para- meters used in predicting the biological aggressiveness and metastatic potential of ccRCC and papillary RCC (Novara et al. 2007; Sukov et al. 2012; Nishikimi et al. 2011), although it lacks prognostic significance for chro- mophobe RCC (Cheville et al. 2012). Imaging assessment of tumor grades in RCC may aid in clinical management decisions. For example, less invasive procedures (e.g., nephron-sparing surgery and radiofre- quency ablation) or close observation may be considered for low grade RCC. There have been few previous reports citing use of magnetic resonance imaging (MRI) to compare Fuhrman grade with imaging characteristics, and the number of cases reported was relatively small (Vargas et al. 2013; Goyal et al. 2012; Rosenkrantz et al. 2010). Computed tomography (CT) is most often used for preoperative evaluation of RCC, and image quality is generally similar across institutions. Therefore, CT may be more applicable in evaluating significant numbers of cases. * Correspondence: Ishigamikousei@aol.com 1 Department of Radiology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA 52242, USA Full list of author information is available at the end of the article a SpringerOpen Journal © 2014 Ishigami et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. Ishigami et al. SpringerPlus 2014, 3:694 http://www.springerplus.com/content/3/1/694