Valerie Vilgrain, MD Dominique Najmark, Marie-Pierre

Vullierme,

#{149} Jean-Francois Fl#{233}jou,MD #{149}Lionel MD #{149}Yves Menu, MD #{149}Marc Zins, MD #{149}Henri Nahum, MD

Focal Nodular MR Imaging in 37 Patients’

Hyperplasia and Pathologic

patients with 48 lesions of focal nodular hyperplasia (FNH) underwent preoperative magnetic resonance (MR) examination and surgical resection. Sixteen lesions were imaged at 0.5 T with Ti- and T2weighted spin-echo sequences; 32 lesions were imaged at 2 T with Tiand T2-weighted spin-echo and gradient-recalled-echo sequences. Contrast material-enhanced MR imaging was performed in 20 lesions. MR finaging failed to depict six tumors that were less than 3 cm in diameter. Typical appearance was present in 18 of the 42 (43%) lesions seen at MR. Atypical lesion features included no scar (n = 15), hypointense scar on T2-weighted images (n 7), pseudocapsule (n = 6), strong hyperintense lesion on T2-weighted images (n = 3), diffuse hyperintensity on Tiweighted images (n 3), and heterogeneous lesion (n = 1). Comparison between findings at MR imaging and at histopathologic examination was performed in 38 lesions: There was good correlation between presence and size of the scar on both examinations. In 13 of 20 (65%) of the hyperintense scars on T2-weighted images, edema was prominent, whereas in five of the seven (7i%) hypointense scars on T2-weighted images, edema was absent or low. Thirty-seven

M

of the pearance

perplasia

terms:

761.3119

Liver, focal nodular hyperplasia, Magnetic resonance (MR), tissue

#{149}

characterization

Radiology

1992;

articles about the apof focal nodular hy-

(FNH)

at magnetic

reso-

nance (MR) imaging include a small number of patients (1-5). Recently, two large series have been published; they made use of different magnetic fields and pulse sequences (6,7). The results showed a marked discrepancy, considering the prevalence of MR imaging characteristics. Furthermore in these series, findings at MR imaging were not correlated with findings at histopathologic examination. The purpose of our study was twofold: to study the characteristics of FNH in a surgical series and to correlate MR findings with histopathologic findings to explain the wide range of appearances of FNH on MR images. MATERIALS Between

AND

METHODS

underwent

1985 and 1991, all the patients

surgical

resection

of the liver

lesion. Multiple reasons led to the decision to perform surgical resection in these 37 patients. Abdominal pain or discomfort and uncertain diagnosis were reasons in some cases, and pregnancy was antici-

in some

women.

The purpose

this study was to compare findings imaging and pathologic examination;

therefore,

only

the patients

who

(mean

age, 35 years;

range,

21-57

one man (aged 24 years, with tory of steroid use). From 1985 to 1987, MR imaging performed From the Departments of Radiology (V.V., L.A., D.N., Y.M., M.Z., M.P.V., H.N.), Pathology (1FF.), and Surgery U.B.), H#{244}pitalBeaujon, 100 bd du G#{233}n#{233}ral Leclerc, 92110, Clichy, France. I

ceived

the 1991 RSNA scientific

assembly.

Re-

11, 1991; revision requested February 10, 1992; revision received April 2; accepted April 7. Address reprint requests to V.V. ©

December

RSNA,

1992

of at MR

had un-

dergone resection were included in this series. These patients induded 36 women

184:699-703

with

in

13 patients

with

a 0.5-T superconducting

tem

(Magniscan;

Medical

Belghiti,

MD

Systems,

General Paris).

years) no his-

16 lesions

Electric the

with 2-mm gap. T2were obtained with TR TE of 50, 100, and 150 matrix, two acquisitions, with 1.6-mm gap. From 1987 to 1991, 24 patients with 32 besions underwent imaging on a 2-T superconducting system (Gyrex; Ebscint, Haifa, Israel). Ti-weighted spin-echo imaging was performed with TR of 450 msec, TE of 15.4 msec, a 140 x 256 matrix, four acquisitions, and 10-mm thickness with 1-mm gap. Gradient-recalled-echo images were

obtained msec,

with

sys-

CGR 0.5-T

TR of 58 msec,

a flip angle

TE of 12

of 40#{176}, a 120 x 220 ma-

tnx, and 10-mm T2-weighted

thickness.

images

TR of 2,000 msec,

were

Double-echo obtained

with

TE of 26 and 80 msec,

a

128 x 256 matrix, two acquisitions, and 10-mm thickness with 1-mm gap. Respiratory artifacts were suppressed by means of respiratory compensation. In addition to these sequences, a bobus of 0.1 mmol of gadopentetate dimeglumine (Magnevist;

Berlin)

per kilogram

was in-

jected through an antecubital vein in the last 17 patients (20 lesions). After the bolus injection, gradient-recalled-echo imaging was started in the plane of the lesion and basted 2 minutes. Then, 3 minutes after the bolus injection a delayed contrast material-enhanced TI-weighted sequence was started. The detection rate of the lesions with

MR imaging

was compared

with

the de-

tection rate with intraoperative US. Surgicab resection of at least one lesion per patient was performed in all patients and in 43 of the 48 lesions. In the remaining five lesions the pathologic proof was obtained

with

histologic

after

surgical

Qualitative

examination

topathobogic

of the tissue

biopsy.

analysis

made in conference (V.V., L.A.)-with diagnosis of FNH

of liver lesions

regarding

was

by two radiologists the knowledge of the but not of the his-

findings-who

consensus

was

imaging With

10-mm thickness weighted images of 1,800 msec and msec, a 256 x 256 and 8-mm thickness

Schenng,

referred to our department with suspected FNH underwent MR imaging. All the besions had been previously detected with ultrasonography (US) or computed tomography (CT). During this period 59 patients were examined; of these patients, 37

and

From

Jacques

#{149}

ofthe Liver: Correlation

OST

pated Index

Arriv#{233},MD MD

the

reached following:

a (a) sig-

nab intensity of liver lesions compared with that of normal liver on each Ti- and T2-weighted and gradient-recalled-echo image

and

Ti- and T2-weighted spin-echo imwere acquired. TI-weighted images were obtained with repetition time (TR) of 300 msec, echo time (TE) of 26 msec, a

Abbreviations:

256

plasia,

of hyperintense

lesions

on T2-

unit, ages

x 256

matrix,

four

acquisitions,

and

TE

=

FNH = focal nodular echo time, TR = repetition

hypertime.

699

weighted images compared with the signab intensity of normal spleen; (b) signal homogeneity; (c) lesion enhancement after bolus injection of gadopentetate dimeglumine; and (d) presence, size, and signal intensity

of the

lesion

contrast-enhanced sity

of the

on

unenhanced

images.

lesion,

signal

sion enhancement, scar were considered

and

Signal

inten-

homogeneity,

le-

and presence secondary

of the features.

The size of the scar was measured. lesions

were

classified

cal. Typical

appearance

according

to the

The

as typical

was

three

or atypi-

determined

criteria

of Mattison

et al (2): (a) isointensity on TI- and T2weighted sequences, (b) a central hyperintense scar on T2-weighted images, and (c) homogeneous signal intensity. The analysis of the resected specimen was performed by a pathologist Q.F.F.)

with

no knowledge

macroscopic items were (b) presence (c) presence

of the MR findings.

b.

At

examination the following assessed: (a) homogeneity, and size of the scar, and of a pseudocapsule. At micro-

scopic examination ysis was performed

semiquantitative of slides stained

hematoxylin-eosin,

chromotrope

lin, and picrosirius.

The two latter

ings

were

considered

The

following

titatively

a.

graded

R, reticu-

specific

conditions on

for

were

a scale

analwith

staincollagen.

semiquan-

from

absent

to

prominent within the scar. No statistical analysis was performed. Occluded vessels were examined. Comparison between findings at MR imaging and at histopathologic examination was made in 38 lesions by a radiologist (V.V.) and the pathologist Q.F.F.) together concerning lesion homogeneity and size, location, and composition of the scar.

d.

C.

Figure 1. Typical age (TR msec/TE

lobe. The lesion

MR msec

(2-T =

contains

unit)

and

450/15.4)

a central

macroscopic shows

findings

a large

of FNH.

isointense

hypointense

mass

scar (arrow).

(2,000/80) shows homogeneous lesion. layed, contrast-enhanced, Ti-weighted

Central scar (arrow) MR image (450/15.4)

the scar (arrowheads). (d) Macroscopic and a large central scar.

view

of the same

(a) TI-weighted

MR

(arrowheads)

of the

(b) T2-weighted

im-

right

MR image

appears hyperintense. (c) Dedemonstrates enhancement of

lesion

shows

a homogeneous

lesion

RESULTS MR imaging depicted 42 of the 48 lesions identified at surgery and at intraoperative US. The mean size of all 48 lesions was 4.5 cm (range, 1.512.0 cm). Nineteen lesions were located in the right lobe, 27 in the left lobe, and two in the caudate lobe. Multiple lesions were present in eight patients (two lesions in six patients, three in one patient, and four in another patient). Six FNH lesions bocated in the left lobe (mean diameter, 2 cm;

range,

1.5-3.0

cm)

ered only at surgery found at MR imaging.

MR

were

and

Imaging

The

aforementioned

characteristics

(Fig

typical la,

ib)

of

Radiology

#{149}

Atypical

(a) Ti-weighted

FNH.

were

MR

foci (arrows). (arrow).

lumine was intravenously injected. On contrast-enhanced gradient-recalled-echo images, all the lesions were hyperintense to the liver 10-30 seconds

MR

present in 18 of 48 (38%) lesions and in 18 of 42 (43%) of the FNH lesions detected at MR examination. In seven of the 18 cases, gadopentetate dimeg700

2.

the lesion contains hyperintense no scar and hemorrhagic spots

not

Results are presented concerning typical and atypical characteristics FNH on MR images.

b.

Figure

discov-

were

a.

after

bolus

injection.

bayed contrast-enhanced, Ti-weighted images, but

one

were

On

de-

spin-echo, all FNH lesions

hyperintense

to the

liver, and in all seven cases, high signab intensity was seen within the scar (Fig

ic).

In four

of the

cases

the

scar

image

(450/15.4)

(2-T

(b) Macroscopic

view

unit)

shows

no

of the same

scar,

lesion

and

shows

was better depicted on contrast-enhanced Ti-weighted images than on T2-weighted images, but no statistical comparison was performed. The remaining lesions (n = 24) had

one

or more

atypical

lesions no scar was Ti- and T2-weighted

In seven tense images

on

findings. identified images

lesions

the scar

Ti- and (Fig 3a).

heavily

was

In 15 on both (Fig 2a).

hypoin-

T2-weighted

September

1992

were

observed

at 2 T. Other

malities-such

abnor-

as a hyperintense

be-

sion on Ti-weighted images (n = 3), strong hyperintensity on T2-weighted images (n = 3), and heterogeneous appearance (n = 1)-were encountered only at 2 T.

Comparison

of MR Findings

Pathologic

Findings at MR imaging and topathobogic examination were pared in 38 cases, representing

b. Figure

3.

Atypical

FNH.

(a) 12-weighted

image

pointense scar (arrow). (b) Macroscopic scar (arrow). Scale indicates centimeters.

view

versus

(1,800/100)

(0.5-T

of the same

lesion

unit)

shows

confirms

a small

the small

lesions

hy-

size of the

and

that

were

seen

on

MR

that were surgically Macroscopicfindings.-In

(71%)

lesions,

a scar

hiscomall the images

resected. 27 of 38 identified at

was

pathologic examination and at MR imaging. The size and location of the scar was well correlated between both examinations (Figs ib, id, 3). The mean size of the scars, determined at macroscopic examination, was 5.5 mm (range, 2-20 mm). In 23 cases the scar was solitary and was located at the center of the FNH, whereas multiple scars were present in two cases and scars were located at the periphery of the lesion in two other cases. In eight of 38 (21%) lesions, no scar was

b. Figure

4.

around

Pseudocapsule

the lesion

shows

fibrosis

around

A peripheral

the

rim

was observed pseudocapsube

patient

surrounding

MR image

mass

(arrow).

Scale

or pseudocapsule

in six patients. was complete

and

FNH.

on Ti-weighted

incomplete

The

signal intensity of the pseudocapsule was low on Ti-weighted images in all cases (Fig 4a). On T2-weighted images

the pseudocapsule was hyperintense in four of the six cases and not visible in the two others. The enhanced Tiweighted images obtained in three patients showed rim enhancement of the

A hypointense

indicates

ages

isointense

(including tense fusely

two

to the

lesions

scars). Three hyperintense

on Ti-weighted lesion tensity images.

had on

hyperim-

spleen

with

hyperin-

lesions were to normal

images

difliver

(Fig 5a). One

heterogeneous signal Ti- and T2-weighted

In 13 of the 24 atypical dopentetate dimegbumine venously

was

injected.

On

hanced

gradient-recalled-echo

images, tense

all the

lesions

in-

lesions, gawas intracontrast-enhyperin-

ages;

in one

hypointense

images,

remained

images.

Field 42 lesions

depicted imaged

on MR

with

middle

the

imaged

at high

27 (33%)

lesions

field strength. However, this difference was not statistically significant (P > .05). No scar was identified in three cases imaged at middle field strength and in 12 cases imaged at high field strength. Hypointense scar depicted

obtained

184

3

scar

were im(2 T). present in imaged at nine of

Volume

Number

the

and 27 strength were lesions and in

observed

#{149}

a or

field strength (0.5 T), aged with high field Typical characteristics nine of the 15 (60%) middle field strength

all FNH

were

enhanced

= =

on

at middle

T2-weighted

field

images

strength

3) and at high field strength 4). Three pseudocapsules

at 0.5 T, and

three

at either

MR

examination. (8%),

a small

imaging

or

In three

other

scar

was

present

at pathologic examination (2-, 3-, and 4-mm diameter, respectively) that was not depicted on MR images.

In 10 cases

on

case

15 were

images,

one

seen

on enhanced

Magnetic

(n (n

but

lesions

view

images. In two cases a scar was detected on images, whereas the scar was either hypointense (n = 1) or was not seen (n = 1) on T2-weighted im-

to liver. On delayed, contrastenhanced, spin-echo, Ti-weighted lesions

is seen

nonenhanced hyperintense enhanced

was were

(arrowheads)

(b) Macroscopic

to liver. not

Of the

lesions were strongly on heavily T2-weighted

and

unit).

centimeters.

scar

pseudocapsule.

Three intense

rim

(0.5-T

hyperintense

The in one

in five.

(a)

(300/26)

found

histologic

were others

Microscopic findings-Histologic analysis of the lesions was

performed

in the 38 cases. All lesions with typical MR characteristics (n = i8) were found to have characteristics typical of FNH at microscopy: homogeneous lesion, no hemorrhage, and no fatty infiltration. Lesions with atypical MR characteristics scopic features mal compression

parenchyma rounding the

had specific microin some cases. Abnorof adjacent hepatic

and mild fibrosis surthe lesion were detected

six rimmed

lesions

Foci of hemorrhage the heterogeneous ing

(Fig

2b).

No

at MR

were lesion

present

the

within

present at MR

hemorrhage

infiltration was found hyperintense lesions images, but sinusoidal the

(Fig

in 4b).

in imag-

or fatty

in the three on Ti-weighted dilatation was

tumor

in two

cases (Fig 5b). In 27 cases the different

of

three

compounds

of the

scar

histologic were

studied

and related to the signal intensity of the scar on T2-weighted images. Quantitative repartition of inflammation and vessels was not related to the signal intensity of the scar. Fibrosis was present in all scars to various degrees. A low content was noted in five

Radiology

70i

#{149}

of 20 hyperintense of seven hypointense weighted images. was

detected

scars and in three scars on T2Abundant fibrosis

in nine

of 20 hyperin-

tense scars and in two of seven hypointense scars on T2-weighted images. A prominent amount of fibrosis was observed in six of 20 hyperintense scars and in two of seven hypointense scars on T2-weighted images. In the 20 hyperintense scars on T2-weighted images, edema was absent in two cases, moderate in five cases, abundant in four cases, and prominent in nine cases. In the seven hypointense scars on T2-weighted images, edema was absent in three cases, moderate in two, abundant in one, and prominent in one. Therefore, edema content was rated as abundant or prominent in 13 of 20 (65%)

hyperintense

scars

and

a. Figure

b. 5.

Atypical

FNH.

(a)

TI-weighted

MR

image

tense mass (arrowheads) and a central hypointense the same lesion shows sinusoidal dilatation within nal magnification, x250).

(450/15.4)

(2-T

unit)

scar. (b) Microscopic the hepatic nodules

shows

a hyperin-

high-power view of (reticulin stain; origi-

as ab-

sent or bow in five of seven (71 % ) hypointense scars on T2-weighted images (Fig 6). DISCUSSION FNH

is a rare

benign

liver

tumor

that is often observed in the 3rd to 5th decades of life. The frequency of this tumor is not well known but has been reported to be 3% in the adult population studied by Karhunen (8). FNH is more

common

than

hepatic

ade-

noma. FNH is a nonencapsulated besion composed of nodules of normal hepatocytes and stellate fibrous bands,

with

edema,

vessels,

bile

Radiology

#{149}

6.

Microscopic

views

of scars

that

were

(a) hyperintense

T2-weighted images. (a) Microscopic low-power view edema (picrosinus stain; original magnification, x40). central scar (same magnification as in a) demonstrates sirius

and

(b) hypointense

of the central (b) Microscopic dense fibrosis

on

scar shows prominent low-power view of the with little edema (picro-

stain).

ducts,

and Kuppfer cells. A central scar is a characteristic feature at macroscopy. Imaging modalities such as angiography and CT demonstrate a homogeneous hypervascularized lesion, but specific diagnosis is rarely possible (9,10). To our knowledge, the first artide about MR imaging of FNH was written by Butch et al (1); they reported mass effect, with tumor nearly isointense with adjacent liver, and the presence of a hyperintense central steblate region on T2-weighted images that corresponded at pathologic examination to the colbagenous scar. Large lesions are most often easily detected on MR images; recognition of small lesions can be difficult due to the relative isointensity of the lesion to the liver. One FNH lesion, 1 cm in diameter, was not found retrospectively in the series published by Mathieu et al (7). In our series, intraoperative US and surgical examination disclosed six of 48 FNH lesions (13%) that were not found at MR imaging; it is interesting to note that all of these lesions were less than 3 cm in diameter and were located in the left 702

b.

a. Figure

lobe of the liver, where motion and vascular artifacts occur more often than in the right lobe. The frequency of the typical appearance of FNH on MR images is not clearly known and varies from 9% to

(seven tense images

of 47) of the lesions were on both Ti- and T2-weighted obtained with the 0.6-T

while

none

50%

the discrepancy was noted only on T2-weighted images. In our series, typical and atypical lesions were not statistically different at middleor high-field-strength imaging. Different TRs used with spin-echo

(2,6).

The

wide

range

in the

fre-

quency of the diagnosis of FNH can be explained in part by a bias of the population (medical vs surgical series). Especially in our surgical series, we observed a fairly high number of patients (24 of 42) with atypical appearance. This is due to the fact that patients underwent surgery when the diagnosis could not be clearly made with preoperative imaging methods. Also, others reasons may exist, including use of different magnetic fields or different TRs with spin-echo sequences, performance of contrastenhanced or nonenhanced imaging, and use of new sequences such as ultrafast dynamic snapshot flash imaging (5,7). The robe of the magnetic field in tissue contrast on Ti- and T2weighted images has been observed by Lee et al (6), who noticed that 47%

tense i.5-T

on images unit. The

sequences intensity. sequences, contrast,

sions

(6).

unit,

to be isoin-

obtained authors

lesions number In our

spin-echo

and

sequences

gave

To our

with suggest

the that

and, therefore, of isointense series,

concerning

debe-

Ti-weighted

gradient-recalled-echo similar

knowledge,

gadopentetate (5,7). cantly

found

also play a robe in lesion Heavily Ti-weighted pulse by providing better tissue increase the number of hy-

pointense crease the

articles

were

isoin-

results.

there

are few

enhancement

dimeglumine

Such enhancement improve lesion-liver

with

in FNH may significontrast

when dynamic imaging is performed. In our study, as in others, the lesions were hyperintense on enhanced imSeptember

i992

ages. Also, the scar was delayed contrast-enhanced images

obtained

enhanced on Ti-weighted

in all cases

(n

in a previous study (7) and one case in our study. Ultrafast imaging

25)

=

in all but

gadolinium-enhanced

MR

enabled evaluation of the fast hemokinetics of FNH by the liver at a frequency of 30 images per minute

(5).

The

specificity

FNH

is not

of MR imaging

well

known

but

in

may

be

high. Only one false-positive case was described by Mathieu et al (7). This lesion

had

typical

MR

characteristics

but was surrounded with an enhanced rim. Pathologic examination demonstrated hepatocelbular carcinoma with a scar. Neither other studies

(1-3,11)

nor

ours

showed

false-positive case. In our series atypical observed cases, the

any

were

(57%). In 15 not seen on

MR images. This finding was observed in three of six cases (50%)

of Mattison et al (2), in i8 of 35 lesions (51%) of Lee et al (6), and in none of the cases of Mathieu et al (7). In our series, comparison of presence and

size of the pathologic

edema,

whereas

showed

absent

hypointense or low

scars

of various

primary

scar at MR imaging and examination showed a re-

hepatocellubar cases of hepatic

edema.

Similar correlation between ings at pathologic examination MR imaging was performed

findand at in central

liver

tumors

(ii). According to findings at the pathologic examination, scars were divided into three subtypes: (a) vascubar scars composed predominantly of vascular channels traversing collagenous tissue; (b) inflammatory scars with edema, necrosis, hypercellularity, and loose (c) collagenous

fibrous

tissue;

and

scars composed predominantly of dense, sclerotic cobbagen. Vascular and inflammatory scars appeared hypointense relative to liver on Ti-weighted images and hyperintense on T2-weighted as collagenous scars

findings

in 24 of 42 cases central scar was

nent scars

tense

relative

images, wherewere hypoin-

to liver

T2-weighted

on both

images.

Rummeny

In the

of the

scars.

and

The

ious typical

and

article

by

in our

1.

study,

4.

ports

the

conclusion

can depict diameter. T2-weighted

that

MR

imaging

a scar greater than 2 mm in Among the 27 scars seen on MR images in our study,

20 were hyperintense and seven were hypointense. Hypointense scar was reported in one FNH lesion (3). In

two cases, hypointense radiating linear areas were associated with hyperintense scar (7). In the latter cases, pathologic examination demonstrated prominent obliterative vascular

perintense Ti-weighted intensity (3%)

were

of the

cases

in a previous

in our

cases,

no

could

perhaps

be the

and

fibrosis,

edema,

inflammation

The

connective

were

distribution

yescarefully

of fibrosis,

inflammation, and vessels was not apparently different in the hyperand hypointense scars. However, edema differed markedly according to the signal

the

intensity

of the

hyperintense

Volume

184

scar.

scars

Number

#{149}

Most

showed

3

of

promi-

of hepatic

parenchyma,

of

nodular

characteriza-

primary

malignant

1987; 148:711-715. H’s’, Saul SF1, Yeager

BA,

MR imaging offocal nodof the liver. J Comput Assist 11:651-654.

1987;

M, Li KCP,

Urhahn

IR,

of he-

WB.

hyperplasia

El Rahman

from

AiR Kressel

of

LE, Francis

MR imaging

hyperplasia:

distinction tumors. ML,

imaging

J Comput

Ros

PR.

Hepatic

R, Klose

KC,

Drobnitzky

hyperplasia:

focal

Magn

M.

Hepatic

diagnosis

by ultra-

fast Cd-DTPA enhanced flash MR. J Comput Assist Tomor 1991; 15:848-851. Lee MJ, Saini S. Hamm B, et al. Focal nodular hyperplasia of the liver: MR findings in 35

proved cases. AJR 1991; 156:317-320. Mathieu D, Rahrnouni A, Anglade MC, et al. Focal nodular hyperplasia of the liver: assesswith

Karhunen mor-like

contrast-enhanced

TurboFLASH Radiology 1991; 180:25-30. PJ. Benin hepatic tumor and tuconditions in man. J Clin Pathol 1986;

39:183-188. 9.

Welch TJ, Sheedy PF, Johnson cal nodular hyperplasia and

CM, hepatic

et al. Foadenoma:

of angiography, CT, US, and scmtigraphy. Radiology 1985; 156:593-595. Mathieu D, Bruneton JN, Drouillard J, CaronPointreau C, Vasile N. Hepatic adenomas and focal nodular hyperplasia: dynamic CT study. Radiology 1986; 160:53-58. comparison

10.

11.

Rummeny

E, Weissleder R, Sironi S. et al. in primary liver tumors: MR feahires, specificity, and pathologic correlation. Radiology 1989; 171:323-326. Itoh K, Nishimura K, Togashi K, et al. Hepa-

Central

12.

scars

tocellular

with

mild fibrosis surrounding the lesion. All the atypical findings observed in our series can mimic hepatic adenoma and hepatocellular carcinoma. Hyperintense signal intensity on Tiweighted images has been reported to occur in 18 of 58 (31%) cases of

focal

hepatic Schiebler

MR

MR imaging.

sion

sels,

study,

and

WD.

ment

images.

In our

vessels

Bree RL, Ensminger

focal nodular

8.

studied. Obliterative vascular changes were noted in both hyperintense and hypointense scars on T2-weighted

in the

5.

7.

the hyperintensity of some hyperintense lesions on Ti-weighted images. It is well known that FNH is a nonencapsulated lesion. However, we observed six cases in which complete or incomplete pseudocapsules were present. In all cases, pathologic examination disclosed abnormal compres-

changes tissue.

of

MR

nodular hyperplasia: new MR findings. Reson Imaging 1989; 7:687-688.

6.

or

cause

Malt RA. hyperplasia. 10:874-877. GM, Quint

Tomogr

is generally hemorrhage,

series,

were

for diagnosis by the presence

Butch RJ, Stark DD, hepatic focal nodular Assist Tomogr 1986; Mattison CR, Glazer

ular

study

surgical

of FNH

dynamic

Axel L, Gefter

fatty infiltration was present. Furthermore, in two of the three cases, the sinusoids were dilated. Intrabesion peliosis

findings

tion and

hy-

hemorrhage

MR

patic

relative to normal liver on images. Such high signal was observed in 12 of 35

(6). The hyperintensity the result of intralesion but

diffusely

tumors.

in our

References

examination.

lesions

T2-

imaging and to compare results with contrast-enhanced and nonenhanced imaging to increase sensitivity while maintaining high specificity. U

2.

discrepancy

on

and size of the scars as demonstrated at pathologic examination. Further studies are needed to assess the role

logic

the

liver

sitivity of MR imaging FNH could be limited

3.

sup-

region

present in 18 of 42 (43%) of the lesions detected at MR. Atypical MR findings, including the absence of scar, were well correlated at histopathobogic examination. This suggests that the sen-

markable correlation in 35 of 38 besions; in the three remaining cases a small scar was detected only at patho-

finding

primary

In conclusion,

could probably be the result of studying different tumors (FNH versus hepatocellular carcinoma and giant hemangioma). In three of 42 (6%) cases in our

This

central

and in some (12,13). A

weighted images has been described in fibrolamellar hepatocellular carcinoma (14). The presence of a capsule or pseudocapsube is suggestive of var-

of contrast-enhanced

Ti-

study, scars with predominant edema had bong T2 TRs. Differences occurred in the significance of hypointense scars on T2-weighted images: low edema content or predominant collagen content

et al (ii)

hypointense

carcinoma adenoma

carcinoma:

13.

1987; Cabata aing

164:21-25. T, Matsui of hepatic

14.

Titelbaum

DS,

Kressel

HY, Burke

lar hepatocellular I Comput Assist

MR imaging.

0, Kadoya adenoma. Hatabu

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M, et al. MR imAJR 1990; 155:1009-

H, Schiebler

DR. Saul

SH.

ML,

Fibrolamel-

carcinoma: MR appearance. Tomogr 1988; 12:588-591.

Radiology

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Focal nodular hyperplasia of the liver: MR imaging and pathologic correlation in 37 patients.

Thirty-seven patients with 48 lesions of focal nodular hyperplasia (FNH) underwent preoperative magnetic resonance (MR) examination and surgical resec...
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