The presence of intralesional fat provides an invaluable tool for narrowing the differential diagnosis for both benign and malignant neoplasms of the abdomen and pelvis. The ability to characterize intralesional fat is further expanded by the ability of magnetic resonance imaging to detect small quantities (intravoxel) of fat. While the presence of intralesional fat can help to provide a relatively narrow set of diagnostic possibilities, depending on the type of fat (macroscopic vs intravoxel) that is present and the organ of origin, radiologists must be aware of uncommon mimickers of pathology, both benign and malignant.
PereiraJMSirlinCBPintoPSCasolaG. CT and MR imaging of extrahepatic fatty masses of the abdomen and pelvis: techniques, diagnosis, differential diagnosis, and pitfalls. Radiographics. 2005;25:69–85. doi:10.1148/rg.251045074.
2.
ÜnalEKaraosmanoğluADAkataDÖzmenMNKarçaaltıncabaM. Invisible fat on CT: making it visible by MRI. Diagn Interv Radiol. 2016;22:133–140. doi:10.5152/dir.2015.15286.
3.
OnurMRTurgutATDograVSMacLennanGT. Adrenal neoplasms. In: DograVMacLennanG, eds. Genitourinary Radiology: Male Genital Tract, Adrenal and Retroperitoneum. London, United Kingdom: Springer; nd: 231–267.
4.
ShettyASSipeALZulfiqarM, et al.In-phase and opposed-phase imaging: applications of chemical shift and magnetic susceptibility in the chest and abdomen. Radiographics. 2019;39:115–135. doi:10.1148/rg.2019180043.
5.
BlakeMAHolalkereNSBolandGW. Imaging techniques for adrenal lesion characterization. Radiol Clin North Am. 2008;46:65–78. doi:10.1016/j.rcl.2008.01.003.
6.
Mayo SmithWWSongJHBolandGL, et al.Management of incidental adrenal masses: a white paper of the ACR Incidental Findings Committee. J Am Coll Radiol. 2017;14:1038–1044. doi:10.1016/j.jacr.2017.05.001.
7.
ChoiYAKimCKParkBKKimB. Evaluation of adrenal metastases from renal cell carcinoma and hepatocellular carcinoma: use of delayed contrast-enhanced CT. Radiology. 2013;266:514–520. doi:10.1148/radiol.12120110.
8.
TariqUPoderLCarlsonDCourtierJJoeBNCoakleyFV. Multimodality imaging of fat-containing adrenal metastasis from hepatocellular carcinoma. Clin Nucl Med. 2012;37:e157–159. doi:10.1097/RLU.0b013e31824439ab.
9.
SchwartzLHMacariMHuvosAGPanicekDM. Collision tumors of the adrenal gland: demonstration and characterization at MR imaging. Radiology. 1996;201:757–760. doi:10.1148/radiology.201.3.8939227.
10.
SchiedaNSiegelmanES. Update on CT and MRI of adrenal nodules. AJR Am J Roentgenol. 2017;208:1206–1217. doi:10.2214/AJR.16.17758.
11.
WooSChoJYKimSYKimSH. Adrenal adenoma and metastasis from clear cell renal cell carcinoma: can they be differentiated using standard MR techniques?Acta Radiol. 2014;55:1120–1128. doi:10.1177/0284185113512301.
12.
JohnsonPTHortonKMFishmanEK. Adrenal imaging with multidetector CT: evidence-based protocol optimization and interpretative practice. Radiographics. 2009;29:1319–1331. doi:10.1148/rg.295095026.
13.
GoldmanSMKenneyPJ. The adrenal glands. In: LeeJKTSagelSSStanleyRJHeikenJP, eds. Computed Body Tomography With MRI Correlation. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006.
14.
KenneyPJWagnerBJRaoPHeffessCS. Myelolipoma: CT and pathologic features. Radiology. 1998;208:87–95. doi:10.1148/radiology.208.1.9646797.
15.
LauSKWeissLM. The Weiss system for evaluating adrenocortical neoplasms: 25 years later. Hum Pathol. 2009;40:757–768. doi:10.1016/j.humpath.2009.03.010.
16.
OutwaterEKBlasbalgRSiegelmanESValaM. Detection of lipid in abdominal tissues with opposed-phase gradient-echo images at 1.5 T: techniques and diagnostic importance. Radiographics. 1998;18:1465–1480. doi:10.1148/radiographics.18.6.9821195.
17.
DelahuntBGrignonDJEbleJN. Tumors of the kidney. In: AminMBGrignonDJSrigleyJREbleJN, eds. Urological Pathology, Philadelphia, PA: Lippincott Williams & Wilkins; 2014.
18.
LimRSFloodTAMcInnesMDFLavalleeLTSchiedaN. Renal angiomyolipoma without visible fat: can we make the diagnosis using CT and MRI?Eur Radiol. 2018;28:542–553. doi:10.1007/s00330-017-4988-4.
19.
HélénonOMerranSParafF, et al.Unusual fat-containing tumors of the kidney: a diagnostic dilemma. Radiographics. 1997;17:129–144. doi:10.1148/radiographics.17.1.9017804.
20.
RichmondLAtriMShermanCSharirS. Renal cell carcinoma containing macroscopic fat on CT mimics an angiomyolipoma due to bone metaplasia without macroscopic calcification. Br J Radiol. 2010;83:e179–e181. doi:10.1259/bjr/46452134.
21.
ChaICartwrightDGuisMMillerTRFerrellLD. Angiomyolipoma of the liver in fine-needle aspiration biopsies: its distinction from hepatocellular carcinoma. Cancer. 1999;87:25–30.
22.
JinzakiMSilvermanSGAkitaHNagashimaYMikamiSOyaM. Renal angiomyolipoma: a radiological classification and update on recent developments in diagnosis and management. Abdom Imag. 2014;39:588–604. doi:10.1007/s00261-014-0083-3.
23.
ChungADSchiedaNFloodTA, et al.Suburothelial and extrinsic lesions of the urinary bladder: radiologic and pathologic features with emphasis on MR imaging. Abdom Imag. 2015;40:2573–2588. doi:10.1007/s00261-015-0467-z.
24.
ThickmanD. Fat within the wall of the urinary bladder: computed tomographic appearance. J Comput Assist Tomogr. 2009;33:695–697. doi:10.1097/RCT.0b013e31818d8de6.
25.
KriegshauserJSConleyCRHentzJG. Bladder wall fat on computed tomography with pathologic correlation. Clin Imag. 2013;37:509–513. doi:10.1016/j.clinimag.2012.10.001.
26.
PhilipATAminMBTamboliPLeeTJHillCERoJY. Intravesical adipose tissue: a quantitative study of its presence and location with implications for therapy and prognosis. Am J Surg Pathol. 2000;24:1286–1290.
27.
KitajimaKKajiYImanakaKSugiharaRSugimuraK. MRI findings of uterine lipoleiomyoma correlated with pathologic findings. AJR Am J Roentgenol. 2007;189:W100–W104. doi:10.2214/AJR.07.2230.
28.
TogashiKNishimuraKItohK, et al.Ovarian cystic teratomas: MR imaging. Radiology. 1987;162:669–673. doi:10.1148/radiology.162.3.3809479.
29.
YamashitaYHatanakaYTorashimaMTakahashiMMiyazakiKOkamuraH.Mature cystic teratomas of the ovary without fat in the cystic cavity: MR features in 12 cases. AJR Am J Roentgenol. 1994;163:613–616. doi:10.2214/ajr.163.3.8079854.
30.
ParkSBKimJKKimKRChoKS. Imaging findings of complications and unusual manifestations of ovarian teratomas. RadioGraphics. 2008;28:969–983. doi:10.1148/rg.284075069.
31.
ParkJYKimDYKimJHKimYMKimYTNamJH. Malignant transformation of mature cystic teratoma of the ovary: experience at a single institution. Eur J Obstet Gynecol Reprod Biol. 2008;141:173–178. doi:10.1016/j.ejogrb.2008.07.032.
32.
JungSELeeJMRhaSEByunJYJungJIHahnST. CT and MR imaging of ovarian tumors with emphasis on differential diagnosis. RadioGraphics. 2002;22:1305–1325. doi:10.1148/rg.226025033.
33.
FotiPVAttinàGSpadolaSCaltabianoRFarinaRPalmucciS, et al.MR imaging of ovarian masses: classification and differential diagnosis. Insig Imag. 2015;7:21–41. doi:10.1007/s13244-015-0455-4.
34.
JeongYYOutwaterEKKangHK. Imaging evaluation of ovarian masses. RadioGraphics. 2000;20:1445–1470. doi:10.1148/radiographics.20.5.g00se101445.
35.
CabarrusMCYehBMPhelpsASOuJJBehrSC. From inguinal hernias to spermatic cord lipomas: pearls, pitfalls, and mimics of abdominal and pelvic hernias. Radiographics. 2017;37:2063–2082. doi:10.1148/rg.2017170070.
36.
ThompsonWM. Imaging and findings of lipomas of the gastrointestinal tract. AJR Am J Roentgenol. 2005;184:1163–1671. doi:10.2214/ajr.184.4.01841163.
37.
HarisinghaniMGWittenbergJLeeWChenSGutierrezALMuellerPR. Bowel wall fat halo sign in patients without intestinal disease. AJR Am J Roentgenol. 2003;181:781–784. doi:10.2214/ajr.181.3.1810781.
38.
CraigWDFanburg-SmithJCHenryLRGuerreroRBartonJH. Fat-containing lesions of the retroperitoneum: radiologic-pathologic correlation. Radiographics. 2009;29:261–290. doi:10.1148/rg.291085203.
39.
LevyADManningMAAl-RefaieWBMiettinenMM. Soft-tissue sarcomas of the abdomen and pelvis: radiologic-pathologic features, part 1—common sarcomas: from the radiologic pathology archives. Radiographics. 2017;37:462–483. doi:10.1148/rg.2017160157.
40.
SinghAKGervaisDAHahnPFSagarPMuellerPRNovellineRA. Acute epiploic appendagitis and its mimics. Radiographics. 2005;25:1521–1534. doi:10.1148/rg.256055030.
41.
KamayaAFederleMPDesserTS. Imaging manifestations of abdominal fat necrosis and its mimics. Radiographics. 2011;31:2021–2034. doi:10.1148/rg.317115046.
42.
BoardmanJKaplanKJHollcraftCMansfieldLTB. Radiologic-pathologic conference of Keller Army Community Hospital at West Point, the United States Military Academy: torsion of the epiploic appendage. AJR Am J Roentgenol. 2003;180:748.
