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European Radiology
Published in: European Radiology 2/2016

01-02-2016 | Urogenital

Angiomyolipoma (AML) without visible fat: Ultrasound, CT and MR imaging features with pathological correlation

Authors: Shaheed W. Hakim, Nicola Schieda, Taryn Hodgdon, Matthew D. F. McInnes, Marc Dilauro, Trevor A. Flood

Published in: European Radiology | Issue 2/2016

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Abstract

Objective

To compare imaging findings with histopathology in AML without visible fat (AMLwvf).

Material and methods

With IRB approval, we identified 18 AMLwvf that underwent CT between 2002-2014. A radiologist measured NECT-attenuation, corticomedullary (CM) and nephrographic (NG) enhancement, echogenicity relative to renal cortex (RC) (N = 5), T2W (T2AML/T2RC) signal-intensity (SI), and chemical-shift SI ([SIIN-PHASE − SIOPPOSED-PHASE]/SIIN-PHASE) indices (N = 6). A pathologist re-evaluated 15/18 AMLwvf for 1) < or > 25 % adipocytes/high-power-field (HPF), 2) “many or few” blood vessels. Comparisons were performed using chi-square and independent t-tests.

Results

73.3 %(11/15) of AMLwvf had <25 % adipocytes/HPF and 86.7 %(13/15) had “many” blood vessels. NECT-attenuation was 41.8(±6.9) HU. 61.1 %(11/18) of AMLwvf were hyper-attenuating and 38.9 %(7/18) iso-attenuating; attenuation was associated with %-adipocytes/HPF, (p = 0.01). CM/NG enhancement were 63.3(±20.8)/51.7(±15.5) HU. 72.2 %(13/18) of AMLwvf had wash-out enhancement, with no association with amount of blood vessels at pathology, (p = 0.68). No difference in echogenicity was noted by histology (p > 0.05). All AMLwvf were T2-hypointense (SI ratio = 0.61 [±0.1]). 2/6 AMLwvf showed SI drop on chemical-shift MRI; both were iso-attenuating and were associated with >25 % adipocytes/HPF (p = 0.04).

Conclusions

AMLwvf are typically T2-hypointense and hyper-attenuating with wash-out enhancement due to abundant smooth muscle and vessels respectively. Iso-attenuating AMLwvf with microscopic fat on MRI contain more adipocytes/HPF.

Key Points

• Five percent of AML do not demonstrate detectable fat on imaging
• These AML are hyperattenuating and T2-hypointense due to abundant smooth muscle
• These AML show washout enhancement without association to vessel count at histopathology
• Iso-attenuating AML with microscopic fat on MRI show >25 % adipocytes/HPF
• The term “AML without visible fat” is proposed to reduce ambiguity
Appendix
Available only for authorised users
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Metadata
Title
Angiomyolipoma (AML) without visible fat: Ultrasound, CT and MR imaging features with pathological correlation
Authors
Shaheed W. Hakim
Nicola Schieda
Taryn Hodgdon
Matthew D. F. McInnes
Marc Dilauro
Trevor A. Flood
Publication date
01-02-2016
Publisher
Springer Berlin Heidelberg
Published in
European Radiology / Issue 2/2016
Print ISSN: 0938-7994
Electronic ISSN: 1432-1084
DOI
https://doi.org/10.1007/s00330-015-3851-8

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