Mi-hyun Kim MD, Presenter: Nothing to Disclose

Jeong Kon Kim MD, Abstract Co-Author: Nothing to Disclose

Hyuck Jae Choi MD, Abstract Co-Author: Nothing to Disclose

Kyoung-Sik Cho MD, Abstract Co-Author: Nothing to Disclose

To evaluate diagnostic performance of MDCT-based scoring system for differentiating angiomyolipoma with minimal fat (AMLmf) from renal cell carcinoma (RCC)

In 48 patients with AMLmfs, 247 with clear cell RCC, 67 with papillary RCC, and 45 with chromophobe RCC, MDCT images were obtained in unenhanced, corticomedullary and early excretory phases. Two radiologists blindly reviewed the ratio of long-to-short tumor diameter (L/S ratio), degree of enhancement, tumor attenuation on unenhanced scan, homogeneity of enhancement, enhancement pattern over time, tumor margin, intratumoral calcification, patient age, and male-to-female ratio. These findings were compared in AMLmf, clear cell RCC, papillary RCC and chromophobe RCC using ANOVA and chi-square tests. Multivariate logistic regression analysis was used to determine the significant predictors for AMLmf. Using these predictors, scoring system was generated to differentiate AMLmf from RCC, of which the diagnostic accuracy was assessed using ROC analysis.

L/S ratio (mean, 1.3 for AMLmf vs. 1.12 – 1.15 for RCCs) was the only finding that was different between AMLmf and RCC but not between RCC subtypes (P < .05). Frequency of strong enhancement, homogeneous enhancement, high attenuation on unenhanced scan and male to female ratio were different not only between AMLmf and RCCs but also between subtypes of RCC (P < .05). According to logistic regression analysis, L/S ratio (beta coefficient, 5.61), high attenuation on unenhanced scan (1.81), homogeneous enhancement (1.15), degree of enhancement on early excretory phase (0.03) and female predominance (2.24) were significant predictors for AMLmf over RCC. Using these predictors, scoring system (0 – 5) was generated to differentiate AMLmf from RCC. The area under ROC curve of scoring system was 0.800 (95% CI, 0.758 – 0.838). The threshold of score 1 yielded the highest Youden’s index as the sensitivity and specificity for diagnosing AMLmf were 81% and 69%. With the threshold of 3, the sensitivity and specificity were 15% and 99%.

As MDCT findings of RCC are variable according to subtypes, scoring system is more desirable for differentiating AMLmf from RCC than single predictor.

With scoring system, some patients with AMLmf may avoid unnecessary surgery with a very high specificity.

Kim, M, Kim, J, Choi, H, Cho, K, MDCT-based Scoring System for Differentiating Angiomyolipoma with Minimal Fat from Renal Cell Carcinoma.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12035593.html