Christian Balthasar Van Der Pol MD, Presenter: Nothing to Disclose

Matthew Donald Fernand McInnes MD, FRCPC, Abstract Co-Author: Nothing to Disclose

Bardia Moosavi MD, Abstract Co-Author: Nothing to Disclose

Trevor A. Flood MD, FRCPC, Abstract Co-Author: Nothing to Disclose

Nicola Schieda MD, Abstract Co-Author: Nothing to Disclose

The purpose of this study was to validate the recent observation that papillary renal cell carcinoma (pRCC) may contain intracellular lipid at chemical shift (CS) MRI, and to determine if this finding is associated with T2 weighted (T2W) imaging characteristics.

With IRB approval, 77 consecutive patients were identified over an 11 year period who underwent MRI prior to surgery with a histologic diagnosis of pRCC. Two abdominal radiologists independently assessed each tumor for the presence of intracellular lipid on CS-MRI. T2W images were evaluated for tumor homogeneity and signal intensity (SI) relative to renal cortex and paraspinal muscle. Inter-observer agreement was calculated using the Kappa coefficient. Discordant cases at CS-MRI were reviewed in tandem to establish consensus. T2 SI ratios (SI.tumor/SI.muscle), CS-SI index (SI.IP-SI.OP)/SI.IP x 100 and tumor-to-spleen SI ratios ((SI.tumor.OP – SI.spleen.OP) /(SI.tumor.IP – SI.spleen.IP)-1) x 100, were measured. Associations between intracellular lipid and T2W characteristics were assessed using chi square test and correlations of parametric data were performed using the Pearson correlation coefficient.

After consensus review, 17% of pRCC contained intracellular lipid, with moderate inter-observer agreement (K=0.41). Homogenous T2 SI was observed in 24.2-33.3% of tumors (K=0.63), 56.1-71.2% were hypointense to renal cortex (K=0.43) and 9.1-21.2% were iso/hypointense to muscle (K=0.17). The median (range) for T2 SI ratio was 2.26 (0.33-8.81), CS-SI index was 3.88 (-208.7-77.03)%, and tumor-to-spleen SI ratio was -40(-530-205)%. No tumor with intracellular lipid was homogeneous on T2 and 92% of tumors were hyperintense to muscle on T2. There was an association between T2 heterogeneity and intracellular lipid (p=0.01-0.04). There was no correlation between T2 SI ratio and tumor-to-spleen SI ratio (B=-0.14, p=0.30) or CS-SI index (B=0.24, p=0.054).

Intracellular lipid is detected in a minority of papillary RCC but does not occur in tumors with homogeneously low T2 signal intensity tumors; findings which may help discriminate pRCC from minimal fat angiomyolipoma.

Minimal fat AML are homogeneously low on T2, overlapping with pRCC; and both may demonstrate intracellular lipid. This study shows that pRCC with intracellular lipid are heterogeneously bright on T2.

Van Der Pol, C, McInnes, M, Moosavi, B, Flood, T, Schieda, N, MR Imaging of Papillary Renal Cell Carcinoma: Does Intracellular Lipid Content Correlate with T2 Weighted (T2W) Imaging Characteristics?.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14005200.html