Hye Na Jung MD, Presenter: Nothing to Disclose

Byung Kwan Park MD, Abstract Co-Author: Nothing to Disclose

Chan Kyo Kim MD,PhD, Abstract Co-Author: Nothing to Disclose

Sung Yoon Park, Abstract Co-Author: Nothing to Disclose

Recently, some studies reported that MRI is useful in differentiating angiomyolipoma (AML) with minimal fat and renal cell carcinoma (RCC). However, most of them compared AML with RCC regardless of histologic subtypes. The purpose of our study was to determine whether MRI features contribute to differentiate AML with minimal fat from each RCC subtype.

Fifteen patients with 17 AMLs and 122 patients with 124 RCCs underwent both CT and MRI, preoperatively. AMLs had no fat tissue identified on CT. All tumors were histologically confirmed by biopsy or surgery. The RCCs were confirmed 91 clear cell, 21 papillary, and 12 chromophobe RCCs. T1 and T2 signal intensity (SI) ratio was defined as ratio of tumor to renal cortex SI on T1- and T2-WI, respectively. Signal intensity index (SII) of tumor was defined as [SI (in) – SI (op)]/[SI (in)] × 100; SI (in) and SI (op) were in-phase and opposed phase tumor SI, respectively. T1 and T2 SI ratios and SII were compared between AML and each RCC subtypes. Kruskal-Wallis test with Dunn test was used for statistical analysis.

The mean T2 SI ratios of AML, clear cell, papillary, and chromophobe RCC were 0.78 ± 0.14 (0.55 – 1.08), 1.01 ± 0.29 (0.41 – 1.83), 0.73 ± 0.26 (0.28 – 1.33), and 0.93 ± 0.23 (0.52 – 1.31), respectively. There was significant difference between AML and clear cell RCC in terms of T2 SI ratio (p<0.05). However, AML was not significantly different from papillary or chromophobe RCC. The mean T1 SI ratios of AML, clear cell, papillary, and chromophobe RCC were 0.93 ± 0.23 (0.57 – 1.64), 1.20 ± 1.51 (0.07 – 10.4), 0.93 ± 0.30 (0.28 – 1.48), and 1.88 ± 3.06 (0.70 – 12.0), respectively. The mean SIIs of AML, clear cell, papillary, and chromophobe RCC were -17.4 ± 40.7 (-103 – 45.6), 5.41 ± 46.7 (-329 – 52.8), -7.03 ± 29.8 (-106 – 29.9), and -12.5 ± 47.3 (-149 – 30.8), respectively. There was no significant difference between AML and each RCC subtype using T1 SI ratio and SII.

AML with minimal fat cannot be definitely differentiated from each RCC subtype using MRI features because histologically heterogeneous RCCs have various MRI features that are significantly overlapped with those of AML with minimal fat.

Preoperative percutaneous biopsy is necessary to avoid unnecessary surgical treatment of AML with minimal fat.

Jung, H, Park, B, Kim, C, Park, S, Comparison of Angiomyolipoma with Minimal Fat and Subtypes of Renal Cell Carcinoma Using T1-weighted, T2-weighted and Chemical Shift MRI.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12028227.html