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.

Tumor morphology and Fuhrman grade are shown in Table 1. Nineteen of 22 (86.4%) cystic ccRCC were low grade (Fuhrman grades 1 or 2) (Figure 1) (Tables 1 and2). All of the three cystic ccRCC with grade 3 were Bosniak IV (Figure 2). There was a significant difference in tumor grade between cystic ccRCC and well-circumscribed ccRCC (P = 0.025). Thirty-eight of 43 (88.4%) infiltrative ccRCC were high grade (Fuhrman grades 3 or 4) (Figure 3). There were significant differences in tumor grades between well-circumscribed (Figure 4) and lobulated ccRCC (Figure 5) (P = 0.018), and between lobulated and infiltrative RCC (P = 0.00029).Figure 1