TEHNIQUES
Multislice CT protocol
Abdominal non-enhanced and contrast enhanced CT (NECT+CECT) was performed in all cases.
All patients received 1,5ml/kg of a nonionic iodine based contrast media (350-370 I mg/ml),
with a power injector flow of 3ml/sec.
CT acquisition was initiated at 30-35 seconds for the arterial phase,
60-90 seconds for portal venous phase and at 180-300 seconds for the late phase,
calculated from the starting point of the injection.
MRI protocol
Abdominal examination with a 1.5 T MR system with body phased array coils and injection of 0,1ml/kg Gd-EOB-DTPA or Gd-BOPTA,
the latter being used in cases of hepatic hemangiomas.
Breath-hold acquisitions contained: three plane localizer,
axial T1 Dual Echo,
axial T2 FSE +/- FS,
coronal with long TE and short TE,
axial 3D-T1 FS without and with Gd injection in a multiphase acquisition (3 phases).
In cases of GD-BOPTA,
an axial and coronal 3D-T1 FS acquisition were performed at 3 minutes after the contrast media injection.
Hepatobiliary phase was performed after 20 minutes for Gd-EOB-DTPA and after 90-120 minutes for Gd-BOPTA respectively.
IMAGING FINDINGS
We retrospectively reviewed the CT and MRI images of patients explored in our department for liver masses,
in a period of 5 years,
in which we found 108 patients to have hepatic tumors with central scar.
The particular CT and MRI features,
in correlation with epidemiological factors,
laboratory findings and the patient's personal history,
guided the diagnosis,
but in some cases a histopathological confirmation was needed.
In our study,
the most common HT with CS were giant hemangioma,
FNH and intrahepatic cholangiocarcinoma ( Fig. 2 ).
Fig. 2: Hepatic tumors with central scar found in our clinic
References: Radiology and Imaging Department, Fundeni Clinical Institute, Bucharest, Romania
According to the imaging aspects and in some cases to the histopathological report,
we classified the hepatic lesions with CS in two different categories,
correlating the morphology of this particular feature with its imaging findings for a systematic approach,
with cases illustrated below (Table 3).
Table 3.
Classification of hepatic lesions with central scar - correlation between the morphology of the CS and the imaging findings
|
|
BENIGNE TUMORS
|
MALIGNANT TUMORS
|
Scar's morphology
|
FNH
|
Heman-gioma
|
Adenoma
|
HCC
FLHC
|
Metas-tases
|
IHC
|
Blood vessels
|
Thrombosis,
cystic degene-ration
|
Hemo-rrhage,
fat,
necrosis
|
Fibrosis
|
Fibrosis
|
Fibrosis
|
Scar's imaging feature
|
NECT
|
Hypo/
isodense
|
Hypodense
|
Hyper/
hypo-dense
|
Hypo-dense
|
Hypo-
dense
|
Hypo-
dense
|
CECT
|
Delayed
|
None
|
None
|
No/
minimal
|
Delayed
|
Delayed
|
MRI T1wi
|
Hypo-intense
|
Hypo-intense
|
Hyper/
hypo-intense
|
Hypo-intense
|
Hypo-intense
|
Hypo-intense
|
MRI T2wi
|
Hyper-intense
|
Hypo/
hyper-intense
|
Hyper-intense
|
Hypo-intense
|
Hypo-intense
|
Hypo-intense
|
MRI
+Gd
|
Delayed
|
None
|
None
|
No/
minimal
|
Delayed
|
Delayed
|
I.
POSITIVE DIAGNOSIS
A.
BENIGNE TUMORS
1.
Focal Nodular Hyperplasia (FNH)
CT:
- hypo/isoattenuating to the surrounding liver parenchyma;
- hyperattenuating on arterial phase and isoattenuating on portal and later phases [13].
MR:
- iso/hypointense on T1wi and iso/hyperintense on T2wi;
- the same pattern of enhancement as on CT images,
with iso/high intensity or ring enhancement in hepatobiliary phase [14].
Central scar:
- composed of blood vessels,
bile ducts and edema within a myxomatous tissue;
- hypointense on T1wi,
hyperintense on T2wi;
- delayed enhancement ( Fig. 3 ).
Fig. 3: Focal nodular hyperplasia. Left liver lobe lesion with central scar, which appears hyperintense on T2FS wi (a), hypointense on T1FS wi (b), with enhancement best seen in the late dynamic phase (c), non-enhancing in hepatobiliary phase (d).
References: Radiology and Imaging Department, Fundeni Clinical Institute, Bucharest, Romania
2.
Giant hepatic hemangioma
Hepatic hemangiomas typically associate a CS in the cavernous type,
in which the lesion measures more than 5cm in diameter.
Imaging aspects:
- on native aquisition: hypoattenuating on CT and hypointense on T1-weighted MR images,
with high signal intensity on T2wi;
- enhanced images: characteristic filling pattern,
with a peripheral nodular enhancement and centripetal progression,
hypointense in hepatobiliary phase.
Central scar:
- composed of areas of hemorrhage,
ischemia and thrombosis,
or zones of cystic degeneration [15];
- unenhanced images: hypoattenuating on CT and low signal on T1 MR wi,
with hypo/hyperintensity on T2wi;
- no enhancement after contrast media administration ( Fig. 4 ).
Fig. 4: Giant hemangioma. Hepatic right lobe mass evaluated CT(left) and MRI(right), with centripetal progressive enhancement, associating a central scar, hypodense (a-asterisk), hyperintense on T2wi (e,j-asterisk), hypointense on T1fs(f-asterisk), with no contrast material uptake (b-d,g-i-asterisk).
References: Radiology and Imaging Department, Fundeni Clinical Institute, Bucharest, Romania
3.
Hepatocellular adenoma
CT:
- isoattenuating,
hypoattenuating (due to fat content) or hyperattenuating (due to intratumoral hemorrhage);
- hyperattenuating in arterial phase,
returning to near isodensity on portal and delayed phases [16].
MRI:
- heterogenous aspect: hypo/hyper/isointense on T1wi and mildy hyperintense on T2wi;
- the tumoral enhancement is the same,
seen on CT images,
with low signal intensity in hepatobiliary phases.
Central scar:
- contains old hemorrhage,
fat and sometimes necrosis [17];
- nonenhanced aquisition: variable aspect with a combination of iso/hypo/hyperdensity on CT images and hypo/hyperintensity on T1/T2 weighted MR images,
relative to the proportion of its morphological contents;
- no enhancement ( Fig. 5 ).
Fig. 5: Hepatocellular adenoma. Hepatic masses with lipid content, associating a central scar, which appears hypointense T1(a,b-asterisk)/hyperintense T2(c-asterisk), without contrast enhancement (d-asterisk).HP: hepatocelullar adenoma.
References: Radiology and Imaging Department, Fundeni Clinical Institute, Bucharest, Romania
B.
MALIGNANT TUMORS
1.
Hepatocelullar carcinoma (HCC)
MRI and CT:
- hypo/isoattenuating to the liver on CT images;
- hyperintense on T2 and usually hypointense on T1 weighted MR images;
- arterial 'wash-in" and portal "wash-out",
in both CT and MRI images;
Central scar:
- contains areas of fibrosis;
- hypoattenuating on CT images and hypointense on T1 and T2 weighted MR images [18];
- no or minimal enhancement ( Fig. 6 ).
Fig. 6: Hepatocelullar carcinoma. Hepatic masses with peripheral wash-in(b)/wash-out(c,d) and central hypodense scar (a-asterisk), with delayed enhancement (b-d-asterisk).HP: hepatocellular carcinoma.
References: Radiology and Imaging Department, Fundeni Clinical Institute, Bucharest, Romania
2.
Fibrolamellar hepatocarcinoma (FLHC)
CT and MRI:
- well circumscribed,
lobulated mass,
with frequent small calcification;
- unenhanced aquisition: hypoattenuating on CT images and iso/hypointense on T1 weighted MR images,
with slightly high signal on T2 wi;
- after contrast material injection: hyperenhancing in arterial phase and iso to hypoenhancing in portal and delayed phases.
Central scar:
- the tumor cells are separated by fibrous bands arranged in a parallel or lamellar distribution in the central zone,
forming the central scar [19];
- hypoattenuating and with low signal intensity on T1 and T2 wi;
- no or minimal enhancement ( Fig. 7 ).
Fig. 7: Fibrolamellar hepatocarcinoma. Multiple liver lesions with peripheral arterial wash-in (b) and subsequent wash-out (c,d), associating a hypodense (a), non-enhancing (b,c,d-asterisk) central scar. Hepatomegaly and liver cirrhosis.
References: Radiology and Imaging Department, Fundeni Clinical Institute, Bucharest, Romania
3.
Liver metastases
The liver is the most common site of metastase and the commones organs of origin are: colon,
stomach,
pancreas,
breast and lung [12].
Imaging aspect:
- unenhanced aquistion: hypo- or isoattenuating on CT images and hyperintense on T2 MR weighted images,
with low signal intensity on T1wi and usually restricted water diffusion (hyperintense in DWI and hypointense in ADC map);
- hypo- or hyperenhancing depending on the morphology of the primary tumor,
with hypointensity in hepatobiliary phase.
Central scar:
- contains areas of fibrosis;
- appears hypoattenuating and hypointense on T2 and T1 wi;
- delayed enhancement ( Fig. 8 ).
Fig. 8: Liver metastase with central scar. Patient with history of colo-rectal cancer and liver metastases. Hypoenhancing (b-d) hepatic lesion near the site of resection, associating a central hypodense scar (a-asterisk), with delayed enhancement (b-d-asterisk). Spleen lesion (c,d-thick arrow).
References: Radiology and Imaging Department, Fundeni Clinical Institute, Bucharest, Romania
4.
Intrahepatic cholangiocarcinoma
The intrahepatic cholangiocarcinoma more common presents as the mass-forming type.
Imaging aspect:
- irregular mass but with well defined contours,
usually located peripherally,
associating biliary tree dilatations and hepatic capsular retraction;
- unenhanced aquisition: hypoattentuating and hypointense T1,
with high signal intensity on T2wi;
- heterogenous minor peripheral enhancement with centripetal gradual filling,
hypointense in hepatobiliary phase and restricted water diffusion (hyperintense in DWI and hypointense in ADC map) [20].
Central scar:
- composed of a variable degree of fibrosis and coagulative necrosis [21];
- hypoattenuating and hypointense on T1 and T2 wi;
- delayed enahancement ( Fig. 9 ).
Fig. 9: Intrahepatic cholangiocarcinoma. Hepatic lesions with capsular retraction and central scar, hyperintense T2fs(a-asterisk), hypointense T1fs(b-asterisk) with progressive enhancement (c-e-asterisk), non-enhancing in HBP(f-asterisk).
References: Radiology and Imaging Department, Fundeni Clinical Institute, Bucharest, Romania
II.
DIFFERENTIAL DIAGNOSIS
Necrosis has imaging features resembling the central scars found in different types of liver tumors,
being the most important differential diagnosis.
Large liver masses outgrow their blood supply,
resulting in hypoxia and central necrosis,
most frequently found in hepatic metastasis [22] ( Fig. 10 ).
Fig. 10: Liver metastases with necrosis. Patient with history of colonic cancer. Right liver lobe mass with hypodense (a-asterisk), non-enhancing central pseudoscar (b-d-asterisk).
References: Radiology and Imaging Department, Fundeni Clinical Institute, Bucharest, Romania
A particular pattern of enhancement,
with peripheral areas of contrast material uptake and central unenhancing zones of necrosis is called the "bull's eye" or "target sign" and is most common found in liver metastases from the gastro-intestinal tract,
hepatic abscesses and hepatic epithelioid hemangioendothelioma [23] ( Fig. 11 ).
Fig. 11: Hepatic epithelioid hemangioendothelioma. Hepatic masses with peripheral enhancement and central non-enhancing necrosis (c,d-asterisk), which appears hyperintense T2wi(a-asterisk), hypointense T1wi (b-asterisk).
References: Radiology and Imaging Department, Fundeni Clinical Institute, Bucharest, Romania