Analysis of contrast-enhanced ultrasound features of hepatocellular adenoma according to different pathological molecular classifications

Abstract

OBJECTIVE:

To explore the specific contrast-enhanced ultrasound (CEUS) features of hepatocellular adenomas (HCA) according to their pathological molecular classifications.

METHODS & MATERIALS:

In this retrospective study, fifty-three histopathologically proved HCA lesions (mean size, 39.7±24.9 mm) were included. Final histopathological diagnosis of HCA lesions were identified by surgical resection (n = 51) or biopsy (n = 2) specimens. CEUS imaging features were compared among four subgroups according to World Health Organization (WHO) 2019 pathological molecular classifications standards. Analysis of variance (ANOVA) were used for statistical analysis of continuous variables. Fisher’s exact test were used for categorical variables. The sensitivity (SE), specificity (SP), and accuracy of CEUS feature in diagnosis of each HCA subtype were calculated and compared.

RESULTS:

Final histopathological diagnosis included HNF-1α inactivated HCAs (H-HCA, n = 12), β-catenin activated HCAs (B-HCA, n = 8), inflammatory HCAs (I-HCA, n = 31), and unclassified HCAs (U-HCA, n = 2). During arterial phase of CEUS, all HCAs were hyper-enhanced, 66.6% (8/12) of H-HCAs and 50% (4/8) of B-HCAs displayed complete hyperenhancement, whereas 58.0% (18/31) of I-HCAs showed centripetal filling hyperenhancement pattern (P = 0.016). Hyper-enhanced subcapsular arteries could be detected in 64.5% (20/31) I-HCAs during early arterial phase. During portal venous and late phase, sustained hyper- or iso-enhancement were observed in 91.7% (11/12) of H-HCAs, while most of I-HCAs (61.3%, 19/31) and B-HCAs (7/8, 87.5%) were hypo-enhanced (P = 0.000). Central unenhanced areas were most commonly observed in I-HCAs (29.0%, 9/31) (P = 0.034).

CONCLUSION:

Depending on its unique imaging features including enhancement filling pattern, hyper-enhanced subcapsular artery and presence of washout, CEUS might provide helpful diagnostic information for preoperative prediction of various HCA molecular subtypes.

Keywords

Hepatocellular adenoma (HCA)contrast-enhanced ultrasound (CEUS)pathological molecular subtype washout differentiate

1 Introduction

Hepatocellular adenoma (HCA) is a benign liver neoplasm caused mainly by proliferative stimulation of hepatocytes [1]. The nature history and pathogenic factors were still poorly understood because of lacking sufficient data [2]. HCAs can be single or multiple, the potential risk factors include women in their child-bearing periods, use of oral contraceptives, anabolic steroids, vascular diseases (e.g. Budd-Chiari syndrome and portal vein shunts), metabolic syndromes and genetic disorders [3, 4].

According to current 2019 World Health Organization (WHO) criteria [5], HCAs were categorized into four distinct subtypes based on histopathological and genetic features, which related to their different clinical outcomes, (1) Inflammatory HCA (I-HCA, 40% – 60%), mutations in several genes eventually leading to the signal transducer and activator of transcription 3 (STAT3) signaling pathway activation. This subtype of HCA was proved to have a highest chance of rupture and bleeding especially for lesions larger than 5 cm [6]. (2) β-catenin-activated HCA (B-HCA, 10% – 15%), a subtype characterized by mutations in β-catenin genes. Malignant transformation into HCC is more common for B-HCA in aged males [4]. (3) Hepatocyte nuclear factor 1α-inactivated HCA (H-HCA, 35% – 40%) or steatosis subtype, mainly due to HNF-1α gene inactivating somatic mutations, which is at minimal risk for complications [7]. (4) Unclassified HCA (U-HCA, 5% – 10%), termed for those without any specific mutations.

Traditionally, surgical resection was recommended for HCAs to avoid spontaneous bleeding and malignant transformation [8]. Nowadays, clinical factors such as molecular subtypes, size, gender and age that related to malignant transformation and rupture are overhanging in management [9, 10]. Surgical resection is now only advised for HCA lesions with size >5 cm. For smaller lesions, certain treatments depend on their molecular subtypes. H-HCAs can be managed conservatively by imaging follow-up 6–12 monthly, while resection is still recommended for B-HCAs and I-HCAs [11]. So the accurate preoperative diagnosis or prediction of subtypes of HCA is essential for clinical decision making and further treatment. However, up till now only limited published studies focused on different imaging features according to their molecular subtypes. Meanwhile most of them were based on contrast-enhanced computerized tomography (CE-CT) or magnetic resonance imaging (CE-MRI) imaging features [12 –17].

Contrast-enhanced ultrasound (CEUS) has been proved to be an unique non-invasive technique for characterization of focal liver lesions noninvasively, with accuracy of 83.1% – 95.8%, sensitivity of 78% – 99% and specificity of 63% – 92% [18 –20]. Compared to CE-CT and CE-MRI, CEUS allows real time continuous observation over the whole process of wash-in and wash-out [21].

Up till now, there is no detailed clinical data study about the various CEUS enhancement patterns of HCA lesions with different pathological molecular subtypes.

The purpose of our retrospective study is to evaluate different CEUS features of histopathologically proved HCAs according to their different pathological molecular subtypes.

2 Patients and methods

2.1 Patients

This study was approved by the research ethics committee of our institution (ethical commitment number B2019-113R). From October 2008 to March 2019, 144 histopathological proved HCA lesions in 136 patients were retrospectively collected.

The inclusion criteria were as follows: (1) B mode ultrasound (BMUS) and CEUS examinations of focal liver lesions were performed preoperatively; (2) No medication or treatment to the suspected HCA lesions before ultrasound examination; (3) Histopathology analysis were performed to confirm the final diagnosis and subtypes of HCA; (4) Patients have complete clinical and laboratory data recorded.

The exclusion criteria were the following: (1) HCA lesions which could not be visible on BMUS; (2) CEUS imaging data were not complete.

Finally, fifty-three hepatic lesions in fifty-three patients (30 male, 23 female; mean age, 37.2±10.6 years) were included in this study. Final histopathological diagnosis of HCA were obtained by surgical resection (n = 51) or biopsy (n = 2) specimens. Molecular subtypes of HCA were classified on the basis of immunohistochemical criteria or genotypes [11].

2.2 Imaging acquisition

Ultrasound examinations were performed using LOGIQ E9 (GE Healthcare, Milwaukee, the United States) (n = 17), iU22 (Philips Healthcare, Amsterdam, the Netherlands) (n = 16), Epiq 7 (Philips Healthcare, Amsterdam, the Netherlands) (n = 12), and Aplio 500 (Toshiba, Otawara, Japan) (n = 8). Each ultrasound examination was performed with a 2.0–5.0 MHz curved-array probe. The mechanical index (MI) was set between 0.06–0.09. First, each lesion was examined by BMUS. Then, color Doppler flow imaging (CDFI) was used to detect blood flow signals inside lesions. After that, CEUS examinations were performed by injecting a dose of 1.0–3.0 mL microbubble contrast agent (SonoVue, Bracco, Milan, Italy) intravenously as a quick bolus via a 20-gauge cannula placed in a cubital vein and followed by 5 ml sterile saline flush. Repeated CEUS were performed 20 minutes late when necessary.

2.3 Imaging analysis

Ultrasound images were reviewed independently by two radiologists with over 10 years’ experience in liver CEUS, who were unaware of the patients’ clinical information. On BMUS, the size, number, shape, echogenicity, margin, and color flow signals of lesions were evaluated. On CEUS, the contrast enhancement features and contrast enhancement patterns of HCA lesions during arterial phase (10–40 s), portal venous phase (45–120 s) and late phase (after 120 s) were evaluated [22]. Including: (1) Enhancement degree (hypo-, iso-, or hyper-enhancement); (2) Enhancement pattern (centrifugal, centripetal, diffuse); Diffuse filling was defined whole lesion appeared hyperenhancement synchronously (Fig. 1C). Centrifugal filling was defined as enhancement initial from the central of lesion and progress to the periphery of the lesion during the early stage of arterial phase (Fig. 2C). Centripetal filling was defined as hyperenhancement initial from periphery area of lesion and gradually enhanced towards the center of the lesion (Fig. 3C). (3) homogeneity of enhancement (homogeneous or heterogeneous); (4) Subcapsular vessel was defined as hyper-enhanced tortuous vascular lying under the capsule of the lesion (Figs. 2C, 4D, arrow). (5) Central unenhanced area was defined as a hypo-enhanced area inside the lesion during the whole enhancement phase (Fig. 2D).

Fig. 1

A 37-year-old woman with biopsy and histopathologically proved Hepatocyte nuclear factor 1α-inactivated HCA. BMUS showed hypoechoic 32 mm diameter hepatic lesion with well-defined margin (a), short rod-like blood flow signals is detected in the perilesional with resistance index (RI) of 0.57 (b). After injection of SonoVue, the lesion showed diffuse hyperenhancement in the early arterial phase (c), and it was homogeneously hyperenhanced in late arterial phase (d), sustained iso-enhancement was boserved in portal venous phase (e) and late phase (f).

Fig. 2

A 47-year-old male with histopathologically proved inflammatory HCA. The lesion showed hypoechoic with ill-defined margin on gray scale(a), rim-like blood flow signals was detected in the perilesional (b). On CEUS the lesion demonstrated heterogeneous centripetal filling with hyper-enhanced subcapsular artery in early arterial phase (c, arrow). Central unenhanced area was also seen in the whole enhancement phases (d, arrow). It showed iso-enhancement in portal venous (e). During late phase, it was slightly incomplete hypo-enhancement (f). Photographs of the excised specimen show a well-defined brown mass with hemorrhage region (g, arrow).

Fig. 3

A 53-year-old male with β-catenin-activated HCA. B mode ultrasound (BMUS) showed 52 mm-diameter hypoechoic lesion in the right lobe of liver (a). Color Doppler showed perilesional blood flow signals with resistance index of 0.52 (b). On CEUS the lesion demonstrated centrifugally hyper-enhanced pattern in early arterial phase (c), it was homogeneous enhancement in late arterial phase (d). The lesion was iso-enhancement in portal venous (e) and hypo-enhancement in late phase (f).

Fig. 4

A 43-year-old man with surgery and histopathologically proved unclassified HCA. The lesion showed hypoechoic on B ultrasound (a) The blood flow signals distributed in the perilesional and intralesional of the lesion (b). On CEUS, the lesion presented homogeneously hyper-enhanced with centripetal filling in early arterial phase (c). Subcapsular vessel was observed in early arterial phase (d, arrow). It showed persistent iso-enhancement in portal venous (e) and late phase (f).

2.4 Statistical analysis

Statistical analysis was performed by SPSS 22.0 software (SPSS, Chicago, IL, USA). Quantitative variables were expressed as mean±standard deviation (SD), and qualitative variables were presented as the number and percentage (%). Analysis of variance (ANOVA) were used for comparison between continuous variables and Fisher’s exact test for categorical variables. The sensitivity (SE), specificity (SP), and accuracy of CEUS imaging features of each HCA subtype were calculated and compared. P < #x003C;< #x200A;0.05 was considered statistically significant.

3 Results

3.1 Clinical characteristics

Clinical features of fifty-three patients were summarized in Table 1. Final histopathological results including H-HCAs (n = 12), B-HCAs (n = 8), I-HCAs (n = 31), and U-HCAs (n = 2). The incidence of H-HCAs in women is higher than other subtypes (P = 0.045). Serum tumor markers including AFP, CEA, and CA199 were normal in all patients.

Table 1
Clinical characteristics of patients included (n = 53)

Characteristics Value (n, %)

Age (years)^a 37.2

Mean body mass index (BMI) 23.5

Sex

Male 30 (56.6)

Female 23 (43.4)

Drug use history

None 49 (92.4)

Oral contraceptive 3 (5.7)

Glucocorticoid 1 (1.9)

Clinical symptoms

Incidental findings 47 (88.7)

Abdominal pain 5 (9.4)

Fever 1 (1.9)

Characteristics	Value (n, %)
Age (years)^a	37.2
Mean body mass index (BMI)	23.5
Sex
Male	30 (56.6)
Female	23 (43.4)
Drug use history
None	49 (92.4)
Oral contraceptive	3 (5.7)
Glucocorticoid	1 (1.9)
Clinical symptoms
Incidental findings	47 (88.7)
Abdominal pain	5 (9.4)
Fever	1 (1.9)

Note: ^aMean±standard deviation. Numbers in parentheses are ranges. Numbers in parentheses are percentages.

3.2 B mode ultrasound features

BMUS features of HCA molecular subtypes and lesion size were summarized in Table 2. On BMUS, mean diameter of HCAs was 39.7±17.2 mm (range 11–150 mm), no difference was found between molecular subtyping (P > #x003E;> #x200A;0.05). Most of HCA lesions were hypoechoic on BMUS with regular shape (71.7%, 38/53), well-defined margin (66.0%, 35/53), homogeneous internal echo (60.4%, 32/53) and low resistance index (RI) of color flow (Mean, 0.53±0.11), while 58.3% H-HCA lesions (7/12) showed hyperechoic (P = 0.031). Calcification and necrosis were observed in 13.2% and 9.4% HCAs, with no difference between groups (P > #x003E;> #x200A;0.05).

Table 2
B mode ultrasound Features of HCA lesions according to molecular subtype (n = 53)

Ultrasound features Total Molecular subtype P value

(n, %) H-HCA B-HCA I-HCA U-HCA

(n = 12) (n = 8) (n = 31) (n = 2)

Echogenicity

Hyper-echoic 13 (24.5) 7 (58.3) 2 (25.0) 4 (12.9) 0 0.031

Iso-echoic 5 (9.5) 1 (8.3) 1 (12.5) 3 (9.7) 0

Hypo-echoic 35 (66.0) 4 (33.3) 5 (62.5) 24 (77.4) 2

Homogeneity

Homogeneous 32 (60.4) 8 (66.7) 5 (62.5) 17 (54.8) 1 0.852

Heterogeneous 21 (39.6) 4 (33.3) 3 (37.5) 14 (45.2) 1

Shape

Regular 38 (71.7) 9 (75.0) 7 (87.5) 21 (67.7) 1 0.619

Irregular 15 (28.3) 3 (25.0) 1 (12.5) 10 (32.2) 1

Margin

Well-defined 35 (66.0) 8 (66.7) 6 (75.0) 20 (64.5) 1 0.917

Ill-defined 18 (34.0) 4 (33.3) 2 (25.0) 11 (35.5) 1

Calcification 7 (13.2) 0 1 (12.5) 6 (11.3) 0 0.251

Necrosis 5 (9.4) 0 1 (12.5) 3 (9.6) 1 0.606

Vascularity pattern

Absence 7 (13.2) 1 (8.3) 2 (25.0) 3 (9.7) 1 0.520

Short rod-like 42 (79.2) 11 (91.7) 5 (62.5) 25 (80.6) 1

Dendritic 4 (7.5) 0 1 (12.5) 3 (9.7) 0

Resistance index 0.53±0.11 0.55±0.10 0.51±0.04 0.55±0.09 0.45 0.128

Mean size (mm) 39.7 (11–150) 30.2 (14–89) 51.4 (21–148) 38.4 (11–121) 78 (42,115) 0.623

Ultrasound features	Total	Molecular subtype	P value
Echogenicity
Hyper-echoic	13 (24.5)	7 (58.3)	2 (25.0)	4 (12.9)	0	0.031
Iso-echoic	5 (9.5)	1 (8.3)	1 (12.5)	3 (9.7)	0
Hypo-echoic	35 (66.0)	4 (33.3)	5 (62.5)	24 (77.4)	2
Homogeneity
Homogeneous	32 (60.4)	8 (66.7)	5 (62.5)	17 (54.8)	1	0.852
Heterogeneous	21 (39.6)	4 (33.3)	3 (37.5)	14 (45.2)	1
Shape
Regular	38 (71.7)	9 (75.0)	7 (87.5)	21 (67.7)	1	0.619
Irregular	15 (28.3)	3 (25.0)	1 (12.5)	10 (32.2)	1
Margin
Well-defined	35 (66.0)	8 (66.7)	6 (75.0)	20 (64.5)	1	0.917
Ill-defined	18 (34.0)	4 (33.3)	2 (25.0)	11 (35.5)	1
Calcification	7 (13.2)	0	1 (12.5)	6 (11.3)	0	0.251
Necrosis	5 (9.4)	0	1 (12.5)	3 (9.6)	1	0.606
Vascularity pattern
Absence	7 (13.2)	1 (8.3)	2 (25.0)	3 (9.7)	1	0.520
Short rod-like	42 (79.2)	11 (91.7)	5 (62.5)	25 (80.6)	1
Dendritic	4 (7.5)	0	1 (12.5)	3 (9.7)	0
Resistance index	0.53±0.11	0.55±0.10	0.51±0.04	0.55±0.09	0.45	0.128
Mean size (mm)	39.7 (11–150)	30.2 (14–89)	51.4 (21–148)	38.4 (11–121)	78 (42,115)	0.623

Note: H-HCA: Hepatocyte nuclear factor 1α-inactivated HCA; I-HCA: Inflammatory HCA; B-HCA: β-catenin-activated HCA; U-HCA: unclassified HCA. P value represents for comparing among H-HCA, I-HCA and B-HCA.

3.3 Contrast-enhanced ultrasound features

Comparison of CEUS features of HCAs according to their subtypes were shown in Table 3. All HCAs were hyper-enhanced in arterial phase of CEUS, centripetal filling (41.5%, 22/53) was the most common enhancement pattern, followed by diffuse (37.7%, 20/53) and centrifugal filling (20.8%, 11/53). H-HCAs (66.6%, 8/12) and B-HCAs (50%, 4/8) mainly displayed diffuse filling pattern, whereas I-HCAs (58.0%, 18/31) mainly showed centripetal filling with subcapsular arteries hyper-enhancement in early arterial phase (P = 0.016). For enhancement patterns in arterial phase of CEUS, 91.7% (11/12) of H-HCAs and 87.5% (7/8) of B-HCAs revealed homogeneous enhancement while 45.2% (14/31) of I-HCAs showed heterogeneous enhancement (P = 0.029).

Table 3
CEUS features of HCA lesions according to molecular subtypes (n = 53)

CEUS features Total Molecular subtype P value

(n = 53) H-HCA B-HCA I-HCA U-HCA

(n = 12) (n = 8) (n = 31) (n = 2)

Arterial phase enhancement degree

Hyper-enhancement 53 (100) 12 (100) 8 (100) 31 (100) 2 -

Iso-enhancement 0 0 0 0

Hypo-enhancement 0 0 0 0

Enhancement pattern

Centrifugal 11 (20.8) 2 (16.7) 3 (37.5) 6 (19.4) 0 0.016

Centripetal 22 (41.5) 2 (16.7) 1 (12.5) 18 (58.0) 1

Diffuse 20 (37.7) 8 (66.6) 4 (50.0) 7 (22.6) 1

Enhancement homogeneity

Homogeneous 36 (67.9) 11 (91.7) 7 (87.5) 17 (54.8) 1 0.029

Heterogeneous 17 (32.1) 1 (8.3) 1 (12.5) 14 (45.2) 1

Portal venous phase

Hyper or Iso-enhancement 31 (58.5) 11 (91.7) 2 (25.0) 17 (54.8) 1 0.006

Hypo-enhancement 22 (41.5) 1 (8.3) 6 (75.0) 14 (45.2) 1

Enhancement pattern in late phase

Hyper or Iso-enhancement 25 (47.2) 11 (91.7) 1 (12.5) 12 (38.7) 1 0.000

Hypo-enhancement 28 (52.8) 1 (8.3) 7 (87.5) 19 (61.3) 1

Central unenhanced area during whole enhancement phases 11 (20.8) 0 1 (12.5) 9 (29.0) 1 0.034

Subcapsular vessels in arterial phase 29 (54.7) 5 (41.7) 3 (37.5) 20 (64.5) 1 0.271

CEUS features	Total	Molecular subtype	P value
Arterial phase enhancement degree
Hyper-enhancement	53 (100)	12 (100)	8 (100)	31 (100)	2	-
Iso-enhancement	0	0	0	0
Hypo-enhancement	0	0	0	0
Enhancement pattern
Centrifugal	11 (20.8)	2 (16.7)	3 (37.5)	6 (19.4)	0	0.016
Centripetal	22 (41.5)	2 (16.7)	1 (12.5)	18 (58.0)	1
Diffuse	20 (37.7)	8 (66.6)	4 (50.0)	7 (22.6)	1
Enhancement homogeneity
Homogeneous	36 (67.9)	11 (91.7)	7 (87.5)	17 (54.8)	1	0.029
Heterogeneous	17 (32.1)	1 (8.3)	1 (12.5)	14 (45.2)	1
Portal venous phase
Hyper or Iso-enhancement	31 (58.5)	11 (91.7)	2 (25.0)	17 (54.8)	1	0.006
Hypo-enhancement	22 (41.5)	1 (8.3)	6 (75.0)	14 (45.2)	1
Enhancement pattern in late phase
Hyper or Iso-enhancement	25 (47.2)	11 (91.7)	1 (12.5)	12 (38.7)	1	0.000
Hypo-enhancement	28 (52.8)	1 (8.3)	7 (87.5)	19 (61.3)	1
Central unenhanced area during whole enhancement phases	11 (20.8)	0	1 (12.5)	9 (29.0)	1	0.034
Subcapsular vessels in arterial phase	29 (54.7)	5 (41.7)	3 (37.5)	20 (64.5)	1	0.271

During portal venous phase of CEUS, sustained hyper- or iso-enhancement was observed in 91.7% (11/12) of H-HCAs, while 45.2% (14/31) of I-HCAs and 75.0% (6/8) of B-HCAs were hypo-enhancement (P = 0.06). During late phase of CEUS, most of H-HCA (91.7%, 11/12) were hyper- or iso-enhanced, about half of I-HCAs (61.3%, 19/31) and most B-HCAs (7/8, 87.5%) were hypo-enhanced (P = 0.000).

Central unenhanced areas were most commonly observed in I-HCAs during the whole CEUS enhancement phases (29.0% in I-HCA, 0% in H-HCA and 12.5% in B-HCA, P = 0.034). Subcapsular vessels could be observed during early arterial phase of CEUS in H-HCAs (41.7%, 5/12), B-HCAs (37.5%, 3/8) and I-HCAs (64.5%, 20/31) groups (P = 0.271).

3.4 Typical CEUS imaging features of HCA with different subtypes

H-HCAs were hyperechoic on BMUS, they typically showed homogeneous hyperenhancement diffusely in arterial phase, hyper- or iso-enhanced in portal venous and late phase (sensitivity, 91.7%; specificity, 75.5%; accuracy, 84.9%, respectively) (Fig. 1).

Centripetal filling with subcapsular arteries hyper-enhancement in early arterial phase were more common in I-HCA. Irregular central unenhanced area could be detected in late arterial phase. Washout during portal venous or late phase are characteristic CEUS features for I-HCAs (sensitivity, 71.0%; specificity, 63.6%; accuracy, 67.9%, respectively) (Fig. 2).

The majority of B-HCA showed hyperenhancement in arterial phase with diffuse filling enhancement pattern, and wash-out in portal venous phase. (sensitivity, 87.5%; specificity, 53.3%; accuracy, 58.5%, respectively) (Fig. 3).

The sample size of unclassified HCA was too tiny to draw any reliable CEUS features.

4 Discussion

Preoperative diagnosis of HCA remains a challenge for clinicians. Depending on its relatively low cost and availability, BMUS is nowadays the first line imaging modality for detection and diagnosis of HCA lesions. But BMUS has limited value in characterization of HCA lesions. In fact, HCA lesions were not an entity, each subtype may carry specific imaging features on CEUS [12].

In our current study, we explored the CEUS imaging findings of HCAs according to their different molecular classification. On CEUS, HCAs were reported to present centripetal or mixed filling enhancement pattern in arterial phase, washout in portal phase or late phase [23, 24]. Also rapid homogeneous hyperenhancement during the arterial phase was reported [25]. Some researchers attempted to explain various CEUS enhancement patterns of HCAs from the point of molecular classification [12]. Delayed washout was reported to be more frequently observed in I-HCA, but characterization of B-HCA and H-HCA was not further analyzed due to their limited simple size [13].

CEUS features of H-HCAs were distinct from other subtypes. Most of H-HCAs appear as hyperechoic lesion on BMUS, which might be caused by fatty degeneration of adenoma cells in this subtype [26]. On CEUS, it showed homogeneous hyperenhancement with diffuse filling pattern in arterial phase. Meanwhile as benign focal liver lesions, most of H-HCAs showed typical hyper- or iso-enhanced in portal venous and late phase. Our result is similar with the results of various studies [6 , 27]. Washout of H-HCA in portal venous or late phase was also reported previously [12, 28]. CEUS provided important dynamic perfusion information for diagnosis of H-HCA. According to literatures, while comparing with the most common hyperechoic benign hepatic tumor hepatic hemangioma, hemangioma always reveals peripheral discontinuous nodular hyperenhancement in arterial phase and remains hyper- or iso-enhancement in the portal venous and late phases [29]. On the contrary, H-HCA shows homogeneous hyperenhancement in arterial phase, which might give us some clues for differential diagnosis preoperatively.

Among all the molecular subtypes of HCAs, I-HCAs was reported to have the highest tendency to bleeding or rupture [11]. Heterogeneous centripetal filling with hyper-enhanced subcapsular artery in early arterial phase and hypo-enhancement in portal venous and late phases were more frequently detected in I-HCAs, which was considered to be characteristic CEUS diagnostic features. Several studies have reported that I-HCAs displayed centripetal enhancement pattern in the early arterial phase, while others described I-HCAs with centrifugal hyper-enhancement [12 , 31]. Centripetal filling enhancement pattern with subcapsular tortuous artery was also reported in 46.2% (12/26) of all HCA lesions previously [25]. Pathologically, different enhancement patterns might be caused by different size of lesions, or related to the variable presence of inflammatory, dilated sinusoids, and dystrophic vessels within I-HCAs [26]. Heterogeneous enhancement was probably caused by the degeneration, necrosis and bleeding within these lesions [25, 32]. The CEUS enhancement pattern might be useful in distinguishing HCAs from other liver tumors such as hepatic hemangioma, or focal nodular hyperplasia (FNH) [6]. In our results, half of I-HCAs demonstrated hypo-enhanced in portal venous and late phase, which overlapped with malignant focal liver lesions, such as hepatocellular carcinoma (HCC). The main differential diagnostic feature of I-HCAs was hyperenhancement patterns in early arterial phase [12, 13]. Since I-HCAs were histologically heterogeneous tumors, the imaging features of I-HCAs were proved to be closely correlated with severity of inflammatory infiltrates and telangiectasias [31]. The typical I-HCAs with marked inflammatory infiltrates and telangiectasias showed persistent enhancement in the delayed phase, while atypical I-HCAs showed washout in portal venous phase and delayed phase.

B-HCAs were rare subtype of HCAs, however it was reported to have malignant transformation trend into HCC [33]. The reported imaging findings of B-HCAs varied considerably [13, 34]. In our study, typical CEUS features of B-HCAs included homogeneous hyperenhancement in arterial phase and rapid washout in the portal venous phase, which makes it impossible to differentiate B-HCAs from well-differentiated HCC [13]. Quantitative perfusion analysis for focal hepatic lesions may be helpful in depicting the mirco-vascularization of HCA and even be able to differentiate HCA subtypes [35]. Dynamic contrast-enhanced ultrasound parameters reflecting portal venous and late phase may differ significantly between HCC and HCA lesions. Otherwise, biopsy is often necessary to reach a correct diagnosis.

Meanwhile unclassified HCAs were also rare, and no typical imaging features was reported [9 , 30].

Previously, HCAs were reported to be hyper-enhanced in the arterial phase and showed washout in portal venous and late phase on contrast–enhanced multiphasic computed tomography [36]. But CE-CT was less sensitive in detecting fat, necrosis, or bleeding, which restricted its applications in differentiating various HCA subtypes [15]. Dynamic contrast-enhanced magnetic resonance imaging (CE-MRI) was considered to be superior to CE-CT in diagnosis of HCA subtypes with liver-specific contrast agent [21]. However, current published studies only focused on imaging features of H-HCA and I-HCA, B-HCA was less explored or reported. Furthermore, liver-specific CE-MRI contrast agents might diffuse through membranes and cause prolonged pseudo enhancement.

Compared with CE-CT/MRI, CEUS enables continuous and real time visualization of whole dynamic wash in and wash out enhancement of HCA lesions [26, 37]. Currently, SonoVue is the only intravascular blood-pool contrast agent widely used in China. Sonazoid is a novel second-generation contrast agent, which has a high affinity with Kupffer cells in the hepatic reticuloendothelial system, making imaging of parenchyma-specific possible [38]. With the use of Sonazoid in the near future, CEUS will be more helpful for preoperative prediction of HCA molecular subtypes.

4.1 Limitations

There were some limitations in our study. Firstly, it was a retrospective study, potential selection bias may exist. Secondly, some CEUS imaging features are size dependent, the correlation with lesions’ size will be further analyzed in our future study.

5 Conclusion

Funding

Supported by Shanghai Municipal Key Clinical Specialty (Grant No. shslczdzk03501)

Supported by Shanghai Municipal Science and Technology Medical Guidance Project (Grant No. 18411967200); Shanghai Municipal Science and Technology Innovation Action Plan Clinical Medicine Project (Grant No. 17411954200); Shanghai Municipal Health and Family Planning Commission Research Project (Grant No. 201840215).

References

Bioulac-Sage

, Sempoux

, Balabaud

. Hepatocellular Adenomas: Morphology and Genomics. Gastroenterol Clin North Am. 2017;46(2):253–72. DOI 10.1016/j.gtc.2017.01.003.

Nault

J C

, Bioulac-Sage

, Zucman-Rossi

. Hepatocellular benign tumors-from molecular classification to personalized clinical care. Gastroenterology. 2013;144(5):888–902. DOI 10.1053/j.gastro.2013.02.032.

Dhingra

, Fiel

M I

. Update on the new classification of hepatic adenomas: clinical, molecular, and pathologic characteristics. Arch Pathol Lab Med. 2014;138(8):1090–7. DOI 10.5858/arpa.2013-0183-RA.

Nault

J C

, Couchy

, Balabaud

, et al. Molecular Classification of Hepatocellular Adenoma Associates With Risk Factors,Bleeding, and Malignant Transformation. Gastroenterology. 2017;152(4):880–94. DOI 10.1053/j.gastro.2016.11.042.

Nagtegaal

I D

, Odze

R D

, Klimstra

, et al. The WHO classification of tumours of the digestive system. Histopathology. 2020;76(2):182–8. DOI 10.1111/his.13975.

Bioulac-Sage

, Sempoux

, Frulio

, et al. Snapshot summary of diagnosis and management of hepatocellular adenoma subtypes. Clin Res Hepatol Gastroenterol. 2019;43(1):12–9. DOI 10.1016/j.clinre.2018.07.007.

Zulfiqar

, Sirlin

C B

, Yoneda

, et al. Hepatocellular adenomas: Understanding the pathomolecular lexicon, MRI features,terminology, and pitfalls to inform a standardized approach. J Magn Reson Imaging. 2019. DOI 10.1002/jmri.26902.

Strauss

, Ferreira

A S

, Franca

A V

, et al. Diagnosis and treatment of benign liver nodules: Brazilian Society of Hepatology (SBH) recommendations. Arq Gastroenterol. 2015;52 (Suppl 1):47–54. DOI 10.1590/S0004-28032015000500003.

van Aalten

S M

, Terkivatan

, de Man

R A

, et al. Diagnosis and treatment of hepatocellular adenoma in the Netherlands: similarities and differences. Dig Surg. 2010;27(1):61–7. DOI 10.1159/000268587.

10.

Deneve

J L

, Pawlik

T M

, Cunningham

, et al. Liver cell adenoma: a multicenter analysis of risk factors for rupture and malignancy. Ann Surg Oncol. 2009;16(3):640–8. DOI 10.1245/s10434-008-0275-6.

11.

EASL Clinical Practice Guidelines on the management of benign liver tumours. J Hepatol. 2016;65(2):386–98. DOI 10.1016/j.jhep.2016.04.001.

12.

Dietrich

C F

, Tannapfel

, Jang

H J

, et al. Ultrasound Imaging of Hepatocellular Adenoma Using the New Histology Classification. Ultrasound Med Biol. 2019;45(1):1–10. DOI 10.1016/j.ultrasmedbio.2018.06.015.

13.

Garcovich

, Faccia

, Meloni

, et al. Contrast-enhanced ultrasound patterns of hepatocellular adenoma: an Italian multicenter experience. J Ultrasound. 2019;22(2):157–65. DOI 10.1007/s40477-018-0322-5.

14.

Laumonier

, Cailliez

, Balabaud

, et al. Role of contrast-enhanced sonography in differentiation of subtypes of hepatocellular adenoma: correlation with MRI findings. AJR Am J Roentgenol. 2012;199(2):341–8. DOI 10.2214/AJR.11.7046.

15.

Wang

, Liu

J Y

, Yang

, et al. Hepatocellular adenoma: comparison between real-time contrast-enhanced ultrasound and dynamic computed tomography. Springerplus. 2016;5(1):951. DOI 10.1186/s40064-016-2406-z.

16.

Schaible

, Stroszczynski

, Beyer

L P

, et al. Quantitative perfusion analysis of hepatocellular carcinoma using dynamic contrast enhanced ultrasound (CEUS) to determine tumor microvascularization. Clin Hemorheol Microcirc. 2019;73(1):95–104. DOI 10.3233/CH-199221.

17.

Wildner

, Schellhaas

, Strack

, et al. Differentiation of malignant liver tumors by software-based perfusion quantification with dynamic contrast-enhanced ultrasound (DCEUS). Clin Hemorheol Microcirc. 2019;71(1):39–51. DOI 10.3233/CH-180378.

18.

Alzaraa

, Gravante

, Chung

W Y

, et al. Contrast-enhanced ultrasound in the preoperative, intraoperative and postoperative assessment of liver lesions. Hepatol Res. 2013;43(8):809–19. DOI 10.1111/hepr.12044.

19.

Dietrich

C F

, Ignee

, Trojan

, et al. Improved characterisation of histologically proven liver tumours by contrast enhanced ultrasonography during the portal venous and specific late phase of SHU508A. Gut. 2004;53(3):401–5. DOI 10.1136/gut.2003.026260.

20.

von Herbay

, Westendorff

, Gregor

. Contrast-enhanced ultrasound with SonoVue: differentiation between benign and malignant focal liver lesions in 317 patients. J Clin Ultrasound. 2010;38(1):1–9. DOI 10.1002/jcu.20626.

21.

Cannella

, Brancatelli

, Rangaswamy

, et al. Enhancement pattern of hepatocellular adenoma (HCA) on MR imaging performed with Gd-EOB-DTPA versus other Gd-based contrast agents (GBCAs): An intraindividual comparison. Eur J Radiol. 2019;119:108633. DOI 10.1016/j.ejrad.2019.08.002.

22.

Claudon

, Dietrich

C F

, Choi

B I

, et al. Guidelines and good clinical practice recommendations for contrast enhanced ultrasound (CEUS) in the liver–update 2012: a WFUMB-EFSUMB initiative in cooperation with representatives of AFSUMB, AIUM, ASUM, FLAUS and ICUS. Ultraschall Med. 2013;34(1):11–29. DOI 10.1055/s-0032-1325499.

23.

Kong

W T

, Wang

W P

, Huang

B J

, et al. Contrast-enhanced ultrasound in combination with color Doppler ultrasound can improve the diagnostic performance of focal nodular hyperplasia and hepatocellular adenoma. Ultrasound Med Biol. 2015;41(4):944–51. DOI 10.1016/j.ultrasmedbio.2014.11.012.

24.

Dietrich

C F

, Schuessler

, Trojan

, et al. Differentiation of focal nodular hyperplasia and hepatocellular adenoma by contrast-enhanced ultrasound. Br J Radiol. 2005;78(932):704–7. DOI 10.1259/bjr/88181612.

25.

Dong

, Zhu

, Wang

W P

, et al. Ultrasound features of hepatocellular adenoma and the additional value of contrast-enhanced ultrasound. Hepatobiliary Pancreat Dis Int. 2016;15(1):48–54.

26.

Dharmana

, Saravana-Bawan

, Girgis

, et al. Hepatocellular adenoma: imaging review of the various molecular subtypes. Clin Radiol. 2017;72(4):276–85. DOI 10.1016/j.crad.2016.12.020.

27.

Zarzour

J G

, Porter

K K

, Tchelepi

, et al. Contrast-enhanced ultrasound of benign liver lesions. Abdom Radiol (NY). 2018;43(4):848–60. DOI 10.1007/s00261-017-1402-2.

28.

Manichon

A F

, Bancel

, Durieux-Millon

, et al. Hepatocellular adenoma: evaluation with contrast-enhanced ultrasound and MRI and correlation with pathologic and phenotypic classification in 26 lesions. HPB Surg. 2012;2012:418745. DOI 10.1155/2012/418745.

29.

D’Onofrio

, Crosara

, De Robertis

, et al. Contrast-Enhanced Ultrasound of Focal Liver Lesions. AJR Am J Roentgenol. 2015;205(1):W56–W66. DOI 10.2214/AJR.14.14203.

30.

Purysko

A S

, Remer

E M

, Coppa

C P

, et al. Characteristics and distinguishing features of hepatocellular adenoma and focal nodular hyperplasia on gadoxetate disodium-enhanced MRI. AJR Am J Roentgenol. 2012;198(1):115–23. DOI 10.2214/AJR.11.6836.

31.

Manichon

A F

, Bancel

, Durieux-Millon

, et al. Hepatocellular adenoma: evaluation with contrast-enhanced ultrasound and MRI andcorrelation with pathologic and phenotypic classification in 26 lesions. HPB Surg. 2012;2012:418745. DOI 10.1155/2012/418745.

32.

van den Esschert

J W

, van Gulik

T M

, Phoa

S S

. Imaging modalities for focal nodular hyperplasia and hepatocellular adenoma. Dig Surg. 2010;27(1):46–55. DOI 10.1159/000268407.

33.

Vyas

, Jain

. A practical diagnostic approach to hepatic masses. Indian J Pathol Microbiol. 2018;61(1):2–17. DOI 10.4103/IJPM.IJPM_578_17.

34.

Ponnatapura

, Kielar

, Burke

, et al. Hepatic complications of oral contraceptive pills and estrogen on MRI: Controversies and update - Adenoma and beyond. Magn Reson Imaging. 2019;60:110–21. DOI 10.1016/j.mri.2019.04.010.

35.

Wiesinger

, Beyer

L P

, Zausig

, et al. Evaluation of integrated color-coded perfusion analysis for contrast-enhanced ultrasound (CEUS) after percutaneous interventions for malignant liver lesions: First results. Clin Hemorheol Microcirc. 2018;69(1-2):59–67. DOI 10.3233/CH-189131.

36.

Brancatelli

, Federle

M P

, Vullierme

M P

, et al. CT and MR imaging evaluation of hepatic adenoma. J Comput Assist Tomogr. 2006;30(5):745–50. DOI 10.1097/01.rct.0000224630.48068.bf.

37.

Cannella

, Brancatelli

, Rangaswamy

38.

Zhai

H Y

, Liang

, Yu

, et al. Comparison of Sonazoid and SonoVue in the Diagnosis of Focal Liver Lesions: A Preliminary Study. J Ultrasound Med. 2019;38(9):2417–25. DOI 10.1002/jum.14940.