Evaluation of T1-Weighted MRI to Detect Intratumoral Hemorrhage Within Papillary Renal Cell Carcinoma as a Feature Differentiating From Angiomyolipoma Without Visible Fat.
OBJECTIVE
The objective of the present study is to determine whether hemorrhage within papillary renal cell carcinoma (RCC) can be detected using T1-weighted MRI and to ascertain whether it can be used to differentiate papillary RCC from angiomyolipoma (AML) without visible fat.


METHODS
A retrospective case-control study compared 11 AMLs without visible fat with 58 papillary RCCs smaller than 5 cm that were evaluated using MRI between 2003 and 2015. Two blinded radiologists subjectively evaluated MR images to identify the presence of intratumoral hemorrhage on the basis of a decrease in signal intensity (SI) on in-phase, compared with opposed-phase, chemical-shift MRI and also on the basis of the SI of the lesion compared with that of the renal cortex on fat-suppressed T1-weighted MRI. A third radiologist established consensus and measured the ratio of the SI of the lesion to that of the renal cortex (hereafter referred to as the "SI ratio") on T2-weighted MRI; the SI loss index, as calculated using the equation [(SItumorIP - SItumorOP) / SItumorOP] × 100, where IP denotes the in-phase image and OP denotes the opposed-phase image; and the SI ratio on fat-suppressed T1-weighted MRI. Analyses were performed using tests of association and ROCs.


RESULTS
When AMLs without visible fat were compared with papillary RCCs, no statistically significant difference in the T2-weighted SI ratio was noted (p = 0.08). Papillary RCCs had a lower mean (± SD) SI loss index (-3.7% ± 17.3%; range, -51.3% to 31.3%) than did AMLs without visible fat (37.8% ± 76.1%; range, -15.6% to 184.4%) (p < 0.001). A mean SI loss index of less than -16% resulted in an AUC of 0.71 (95% CI, 0.52-0.91), with a sensitivity and specificity of 22.8% and 100%, respectively, for the diagnosis of papillary RCC. After consensus review, none of the AMLs without visible fat and 16 of the 58 papillary RCCs (27.6%) were found to have a decrease in SI on subjective analysis (p = 0.06, κ = 0.60). Between groups, no differences were noted in the SI ratio on fat-suppressed T1-weighted MRI (p = 0.58) or in the SI observed on subjective analysis of fat-suppressed T1-weighted MRI (p = 0.20, κ = 0.48).


CONCLUSIONS
The presence of intratumoral hemorrhage within papillary RCC is a specific feature that differentiates papillary RCCs from AMLs without visible fat. Subjective analysis may be more clinically appropriate than chemical-shift MRI because of limitations in the quantitative measurement of T2* signal with the use of chemical-shift MRI.
1 Department of Medical Imaging, The Ottawa Hospital, The University of Ottawa, 1053 Carling Ave, Ottawa, ON K1Y 4E9, Canada.
Catherine A
CA
Murray
1 Department of Medical Imaging, The Ottawa Hospital, The University of Ottawa, 1053 Carling Ave, Ottawa, ON K1Y 4E9, Canada.
Matthew
M
Quon
1 Department of Medical Imaging, The Ottawa Hospital, The University of Ottawa, 1053 Carling Ave, Ottawa, ON K1Y 4E9, Canada.
Matthew D F
MD
McInnes
1 Department of Medical Imaging, The Ottawa Hospital, The University of Ottawa, 1053 Carling Ave, Ottawa, ON K1Y 4E9, Canada.
Christian B
CB
van der Pol
2 Department of Anatomical Pathology, The Ottawa Hospital, The University of Ottawa, Ottawa, ON, Canada.
Shaheed W
SW
Hakim
2 Department of Anatomical Pathology, The Ottawa Hospital, The University of Ottawa, Ottawa, ON, Canada.
Trevor A
TA
Flood
1 Department of Medical Imaging, The Ottawa Hospital, The University of Ottawa, 1053 Carling Ave, Ottawa, ON K1Y 4E9, Canada.
Nicola
N
Schieda
D018207:Angiomyolipoma / Q000000981:diagnostic imaging*; D001706:Biopsy; D002291:Carcinoma, Papillary / Q000473:pathology*; D002292:Carcinoma, Renal Cell / Q000473:pathology*; D016022:Case-Control Studies; D003937:Diagnosis, Differential; D005260:Female; D006470:Hemorrhage / Q000000981:diagnostic imaging*; D006801:Humans; D007680:Kidney Neoplasms / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies
MRI; angiomyolipoma; hemorrhage; papillary; renal cell carcinoma