Enhancement patterns of hepatocellular carcinoma at contrast-enhanced US: comparison with histologic differentiation.
OBJECTIVE
To retrospectively compare the arterial and portal venous phase enhancement patterns of hepatocellular carcinoma (HCC) at contrast material-enhanced ultrasonography (US) with the degree of HCC histologic differentiation.


METHODS
This study was approved by the research ethics board, and informed consent was obtained. The study population included 112 consecutive patients (91 men, 21 women; aged 25-86 years) with 112 histologically proved HCCs: 23 well differentiated, 77 moderately differentiated, and 12 poorly differentiated. All underwent continuous real-time low-mechanical-index contrast-enhanced US from wash-in of contrast material to 300 seconds by using a blood-pool microbubble agent. Initial image interpretation included arterial enhancement, dysmorphic intratumor arteries, and presence and time of negative enhancement (washout). Enhancement patterns were compared with histologic differentiation by using the Fisher exact test.


RESULTS
In the arterial phase, 97 of 112 (87%) HCCs showed hypervascularity, with a significantly higher proportion in moderately differentiated HCCs (74 of 77, 96%) when compared with well- (14 of 23, 61%; P<.001) and poorly differentiated HCC (nine of 12, 75%; P<.004). Eight of 112 (7%) were isovascular and seven (6%) were hypovascular. Dysmorphic arteries were seen in 81 (72%) HCCs. Of 97 hypervascular tumors, only 42 (43%) showed typical washout by 90 seconds. Late washout appeared in 25 (26%) HCCs in the 91-180 seconds phase and in 21 (22%) in the 181-300 seconds phase. The remaining nine showed no washout up to 300 seconds and seven (78%) were well-differentiated HCCs.


CONCLUSIONS
Moderately differentiated HCC generally shows classic enhancement features, while well- and poorly differentiated tumors account for most atypical variations. Extended observation in the portal phase is important as late washout occurs with slightly more frequency than washout in the conventionally defined portal venous phase.
Jang
Hyun-Jung
HJ
Department of Medical Imaging, University of Toronto, Toronto General Hospital, 585 University Ave, Toronto, ON, Canada M5G 2N2. hyun-jung.jang@uhn.on.ca
Kim
Tae Kyoung
TK
Burns
Peter N
PN
Wilson
Stephanie R
SR
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging* / Q000473:pathology; D003287:Contrast Media / Q000008:administration & dosage; D005260:Female; D005466:Fluorocarbons / Q000008:administration & dosage; D006801:Humans; D007275:Injections, Intravenous; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014463:Ultrasonography
D003287:Contrast Media; D005466:Fluorocarbons; C042852:perflutren