Hepatocellular carcinoma with a pseudocapsule on gadolinium-enhanced MR images: correlation with histopathologic findings.
OBJECTIVE
To evaluate the characteristics of hepatocellular carcinoma (HCC) with a pseudocapsule on dynamic magnetic resonance (MR) images.


METHODS
The institutional review board approval was obtained, and the requirements for informed consent were waived for this retrospective study. Dynamic MR studies of surgically resected 106 HCCs in 93 patients were retrospectively reviewed. A false-positive fibrous capsule (FC) on dynamic MR images was considered to be a pseudocapsule. Pathologic specimens of HCCs with a pseudocapsule were reviewed. The differences in size, tumor grade, the degree of liver fibrosis and background liver diseases, and the incidence of vascular invasion were compared between HCCs with a pseudocapsule on MR images and those with FC at histologic examination by using Student t, Kruskal-Wallis, and chi(2) tests.


RESULTS
The sensitivity, specificity, and accuracy of dynamic MR in the diagnosis of histologic FC were 94.0% (47 of 50), 73.2% (41 of 56), and 83.0% (88 of 106), respectively. There were 15 (14.2%) HCCs with a pseudocapsule. The pathologic specimens suggested possible causes of the pseudocapsule that included prominent sinusoids (n = 6), peritumoral fibrosis mimicking bridging fibrosis (n = 3), and both (n = 5). In one case, the capsulated HCC was surrounded by a well-differentiated HCC component. The mean size of a HCC with a pseudocapsule tended to be smaller than that with histologic FC, although it was not significant (mean +/- standard deviation: 2.8 cm +/- 1.0 vs 3.5 cm +/- 2.0, P = .09). Liver cirrhosis was less frequent in HCCs with a pseudocapsule than in those with a histologic FC (one of 14 [7.1%] vs 20 of 49 [40.8%], P < .05). The tumor grades were not significantly different, and the incidence of vascular invasion after standardizing the tumor size (<or=4 cm) was similar (five of 14 [35.7%] vs 12 of 37 [32.4%]).


CONCLUSIONS
Dynamic MR imaging is accurate in depicting FC in HCCs. HCC with a pseudocapsule at MR possibly consists of peritumoral sinusoids and/or fibrosis. The pseudocapsule may be similar to histologic FC in terms of tumor invasiveness.
Ishigami
Kousei
K
Departments of Clinical Radiology, Anatomic Pathology, and Surgery and Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan. Ishigamikousei@aol.com
Yoshimitsu
Kengo
K
Nishihara
Yunosuke
Y
Irie
Hiroyuki
H
Asayama
Yoshiki
Y
Tajima
Tsuyoshi
T
Nishie
Akihiro
A
Hirakawa
Masakazu
M
Ushijima
Yasuhiro
Y
Okamoto
Daisuke
D
Taketomi
Akinobu
A
Honda
Hiroshi
H
D000328:Adult; D000368:Aged; D006528:Carcinoma, Hepatocellular / Q000175:diagnosis* / Q000473:pathology; D016009:Chi-Square Distribution; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D008103:Liver Cirrhosis / Q000175:diagnosis* / Q000473:pathology; D008113:Liver Neoplasms / Q000175:diagnosis* / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric
D003287:Contrast Media; D019786:Gadolinium DTPA