Multislice spiral computed tomography signs of invasion of the renal capsule by renal cell carcinoma

Capsular invasion is frequently detected in localized renal cell carcinoma (RCC) specimens and is associated with a poor prognosis, but the pretreatment imaging features are poorly known. This study aimed to explore the positions and margin types of RCC and various computed tomography (CT) signs, as well as the correlations with the presence/absence of RCC invasion of the renal capsule. This was a retrospective study of 158 consecutive patients treated for pathologically confirmed RCC between January 2013 and December 2016 at the Nantong University Affiliated Hospital. The patients were divided into the capsule invasion and noninvasion groups. The CT signs were analyzed (position type, margin type, and CT findings in the perirenal fat). There were 92 (58.2%) men and 66 (41.8%) women; mean age was 59.1 ± 12.8. Renal capsule invasion was confirmed in 45 cases. There was no difference in the position types between the 2 groups (all P > .05). The smooth margin was more common in the noninvasion group (53.1% vs 15.6%, P < .01). The deep lobulated type and the saw tooth sign were more common in the invasion group (57.8% vs 7.1%; and 40.0% vs 6.2%; both P < .01). The deep lobulated (OR = 2.03, 95%CI: 1.21–3.39, P = .007) and saw tooth (OR = 1.036, 95%CI: 1.008–1.065, P = .011) signs were independently associated with renal capsule invasion. Smooth tumor margin suggests the absence of renal capsule invasion, while the deep lobulated and the saw tooth signs strongly suggest the presence of renal capsule invasion in patients with RCC.