The relationship between chemical shift MRI findings and histological grade in clear cell renal cell carcinoma

To evaluate the diagnostic performance of percentage signal intensity (SI) drop on chemical-shift magnetic resonance imaging (MRI) for distinguishing Fuhrman grade 1 from Fuhrman grades 2-4 clear-cell renal cell carcinoma (ccRCC).

This retrospective multicenter study included 85 patients with histopathologically confirmed ccRCC who underwent preoperative 1.5-T MRI including chemical-shift sequences between 2016 and 2024. Percentage tumour-to-spleen SI drop was calculated from in-phase and opposed-phase images. Tumours were classified as Fuhrman grade 1 (n = 30) or Fuhrman grades 2-4 (n = 55), based on grades recorded in the original surgical pathology reports. MRI findings were compared between groups, and ROC curve analysis was performed to evaluate the discriminatory performance of percentage SI drop.

Percentage SI drop was significantly greater in Fuhrman grade 1 tumours than in Fuhrman grades 2-4 tumours [40.0% (IQR, 25.4-54.2) vs. 17.4% (IQR, 5.9-29.2); p = 0.003]. Fuhrman grades 2-4 tumours were significantly larger than grade 1 tumours [46 mm (IQR, 28-74) vs. 39 mm (IQR, 30-49); p = 0.01], whereas tumour composition did not differ significantly (p = 0.08). ROC analysis showed modest discriminatory performance (AUC, 0.695; 95% CI, 0.566-0.824; p = 0.003). A percentage SI drop cut-off of ≥ 27.8% yielded 66.7% sensitivity and 67.3% specificity for identifying Fuhrman grade 1 tumours.

Percentage SI drop was greater in Fuhrman grade 1 than in Fuhrman grades 2-4 ccRCCs, but discrimination was modest and incremental value beyond tumour size was not established. These findings are limited to an exploratory comparison using historical Fuhrman grades and cannot be extrapolated to contemporary World Health Organization/International Society of Urological Pathology (WHO/ISUP) grading.