AJR 2000; 174:1571-1574
© American Roentgen Ray Society
Atypical Inside-Out Pattern of Hepatic Hemangiomas
Si-yeon Kim1,
Jae-Joon Chung,
Myeong-Jin Kim,
Sumi Park,
Jong Tae Lee and
Hyung Sik Yoo
1
All authors: Department of Diagnostic Radiology and Research Institute of
Radiological Science, Yonsei University College of Medicine, #134
Schinchon-dong, Seodaemun-ku, Seoul 120-752, South Korea.
Received July 14, 1999;
accepted after revision October 12, 1999.
Address correspondence to J.-j. Chung.
Introduction
The imaging characteristics of hepatic hemangioma have been well
established, requiring few imaging procedures for the diagnosis of this common
benign hepatic tumor. However, some atypical imaging findings of hepatic
hemangioma have also been reported
[1,
2]; for example, incomplete
central enhancement of hemangioma or isoattenuation of the lesion compared
with the surrounding normal hepatic parenchyma on delayed images of dynamic
studies. We report two patients with centrifugal enhancement patterns on
dynamic contrast-enhanced CT and MR imaging.
Case Report
Case 1
A 45-year-old woman was admitted for evaluation of hepatic masses that were
incidentally discovered during routine screening. Her liver function tests had
normal findings and her test for hepatitis B antibody was positive. Abdominal
sonography revealed two masses in segments II and VIII of the liver
[3], measuring 3 cm and 2.5 cm
in diameter, respectively (Figs.
1A and
1B). Both masses were well
delineated and appeared hypoechoic with posterior acoustic enhancement; one
mass had a central echogenic area and the other had a more focal central
hyperechogenicity. Vascular flow signals were not detected on color Doppler
sonography in or around the masses.
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Fig. 1A. —45-year-old woman with two cavernous hepatic hemangiomas.
Sonographic images reveal 2.5-cm (arrow, A) and 3-cm
(arrow, B) hypoechoic masses in segments VIII and II of liver.
Note central echogenic area.
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Fig. 1B. —45-year-old woman with two cavernous hepatic hemangiomas.
Sonographic images reveal 2.5-cm (arrow, A) and 3-cm
(arrow, B) hypoechoic masses in segments VIII and II of liver.
Note central echogenic area.
|
|
On dynamic CT, no significant enhancement was noted in the lesions during
the early arterial phase, but gradual opacification from the center to the
periphery (centrifugal direction) occurred during the portal and delayed
venous phases. The edges of the lesions appeared unenhanced on 5-min delayed
images.
The masses had low signal intensity on T1-weighted MR images and high
signal intensity on T2-weighted MR images
(Fig. 1C). Gadolinium-enhanced
dynamic MR images (Figs.
1D,1E,1F,1G)
revealed gradual centrifugal enhancement (except for the tumoral edges),
similar to dynamic CT findings. Selective hepatic angiography revealed no
definite evidence of tumor vascularity or staining or filling defect on either
arterial or capillary phases.
99mTc-labeled RBC radionuclide images revealed no increased or
decreased radioactivity in the liver on early dynamic images but revealed
pooling of radiotracer in segments II and VIII on delayed images.
Single-photon emission computed tomography (SPECT) showed increased uptake
lesions at corresponding areas of the liver. Therefore, the two hepatic masses
were radiologically confirmed as hemangiomas with atypical imaging
findings.
Case 2
A 32-year-old man was admitted for evaluation of a hepatic mass that was
discovered on abdominal sonography during a routine examination. A two-phase
abdominal CT scan was obtained. The scan revealed a 2.5-cm lobulated mass in
the boundary area between segments V and VIII
[3]. The mass had low density
with central enhancing foci on arterial phase images and centrifugal
enhancement with a peripheral unenhanced portion on 5-min delayed images
(Figs. 2A and
2B). The lesion had low signal
intensity on T1-weighted MR images and high signal intensity on T2-weighted MR
images (Figs. 2C and
2D). Dynamic MR images were
obtained after gadopentetate dimeglumine injection; on these images, the
lesion had a centrifugal enhancement pattern (Figs.
2E,2F,2G,2H).
The peripheral rim portion remained unenhanced on images with up to a 5-min
delay.
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Fig. 2B. —32-year-old man with hepatic mass at boundary area between segments
V and VIII of liver. On delayed image, mass shows more centrifugal enhancement
with some peripheral unenhancing portions.
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Fig. 2C. —32-year-old man with hepatic mass at boundary area between segments
V and VIII of liver. Mass has high signal intensity on T2-weighted MR image
(C) and low signal intensity on T1-weighted MR image (D).
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Fig. 2D. —32-year-old man with hepatic mass at boundary area between segments
V and VIII of liver. Mass has high signal intensity on T2-weighted MR image
(C) and low signal intensity on T1-weighted MR image (D).
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Fig. 2E. —32-year-old man with hepatic mass at boundary area between segments
V and VIII of liver. Dynamic MR images reveal centrifugal enhancement pattern
of mass, which has peripheral unenhancing portion on 5-min delayed image
(H).
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Fig. 2F. —32-year-old man with hepatic mass at boundary area between segments
V and VIII of liver. Dynamic MR images reveal centrifugal enhancement pattern
of mass, which has peripheral unenhancing portion on 5-min delayed image
(H).
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Fig. 2G. —32-year-old man with hepatic mass at boundary area between segments
V and VIII of liver. Dynamic MR images reveal centrifugal enhancement pattern
of mass, which has peripheral unenhancing portion on 5-min delayed image
(H).
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Fig. 2H. —32-year-old man with hepatic mass at boundary area between segments
V and VIII of liver. Dynamic MR images reveal centrifugal enhancement pattern
of mass, which has peripheral unenhancing portion on 5-min delayed image
(H).
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Discussion
The dynamic distribution of contrast material in the extracellular space
(vascular and interstitial space) has been well documented
[4]. After 1 min, 50% of
contrast material moves from the vascular space to the interstitial space, and
after 5 min, 80% moves. Equilibrium between the two spaces is attained in 2-5
min. After that, the contrast material returns to the vascular space
[4]. Peripheral enhancement
within 2 min of bolus injection is caused by the accumulation of contrast
material in the vascular lakes
[5]. The delayed enhancement of
hemangiomas and some malignant neoplasms have different mechanisms. The
delayed enhancement of hemangiomas is probably caused by the longer retention
of contrast material in large intravascular spaces, resulting from slow flow,
puddling, and partial thrombosis
[6]. Cholangiocarcinoma and
some metastatic liver tumors contain abundant fibrous tissues. Contrast
material is retained by the fibrous stroma because of the large interstitial
spaces in the fibrous tissues and the slow back-diffusion of contrast media in
the vascular space [7,
8]. Hemangiomas with rapid
enhancement on arterial phase images have large vascular spaces with thin
intervening septa. Hemangiomas with delayed contrast enhancement have smaller
vascular channels with a large portion of fibrous interstitial spaces
[9].
The specificity of scintigraphy and 99mTc-labeled RBC
radionuclide scanning with SPECT is nearly 100% in the diagnosis of hepatic
hemangioma.
Although we did not obtain confirmatory pathologic specimens, our patients'
atypical imaging findings probably resulted from the variable structural
features of hepatic hemangiomas. Fibrosis of hepatic hemangiomas occurs
commonly inside the bodies of tumors, beginning in the center and extending
peripherally in variable degrees
[5]. In our patients, the
histologic findings of hemangiomas revealed a central area composed of
numerous vascular spaces, which showed central echogenicity on sonography and
early and prolonged enhancement on dynamic bolus CT. The peripheral portions
of the lesions had a predominantly fibrous component and showed
hypoechogenicity on sonography and delayed enhancement on dynamic CT.
Typical radiographic characteristics of hepatic hemangiomas are well
established and extremely specific; however, intratumoral structural variation
may cause unusual imaging features. More reports about the
radiographic-histologic correlation of hepatic hemangiomas are needed to draw
further conclusions.
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Introduction
Case Report
