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[Background] Technetium-99m-galactosyl human serum albumin scintigraphy is preferred for assessing the liver functional reserve in patients undergoing hepatectomy, but its superiority over computed tomography volumetry after portal vein embolization and subsequent hepatectomy remains elusive. We aimed to compare technetium-99m-galactosyl human serum albumin scintigraphy with conventional computed tomography volumetry for predicting posthepatectomy liver failure in patients after portal vein embolization. [Methods] This retrospective study analyzed 152 consecutive patients who underwent hepatobiliary cancer resection after portal vein embolization between 2006 and 2021. Posthepatectomy liver failure was graded according to the International Study Group of Liver Surgery criteria. The predictive abilities for posthepatectomy liver failure were compared between the future remnant uptake (%) by technetium-99m-galactosyl human serum albumin scintigraphy and the future remnant volume (%) by computed tomography volumetry. [Results] Future remnant uptake (%) was significantly greater than future remnant volume (%) after portal vein embolization (47.9% vs 40.8%; P < .001), while the values were comparable before portal vein embolization (32.7% vs 31.2%; P = .116). Receiver operating characteristic curve analysis revealed that post–portal vein embolization future remnant volume (%) had a significantly higher area under the curve than post–portal vein embolization future remnant uptake (%) (0.709 vs 0.630; P = .046) for predicting posthepatectomy liver failure. Multivariable analysis revealed that post–portal vein embolization future remnant volume (%) independently predicted posthepatectomy liver failure, but future remnant uptake (%) did not. Although the incidence of posthepatectomy liver failure grade ≥B was 17.8% when indocyanine green–clearance of the future liver remnant based on both future remnant volume (%) and future remnant uptake (%) was ≥0.05, it was higher in other combinations: 55.6% for indocyanine green clearance of the remnant volume ≥0.05/indocyanine green clearance of the remnant uptake ≤0.05; 50.0% for indocyanine green clearance of the remnant volume ≤0.05/indocyanine green clearance of the remnant uptake ≥0.05; and 50% for indocyanine green clearance of the remnant volume ≤0.05/indocyanine green clearance of the remnant uptake ≤0.05. [Conclusions] Technetium-99m-galactosyl human serum albumin scintigraphy is not superior to computed tomography volumetry for assessing the future liver remnant in patients undergoing major hepatectomy after portal vein embolization.

To explore the incidence of early bifurcation of the right hepatic artery (RHA) and the right posterior hepatic artery (RPHA), which is crucial in right lobe graft (RLG) and right posterior sector graft (RPSG) procurement for living-donor liver transplantation.Early bifurcation of the hepatic artery tends to induce oversight of one of the bifurcated arteries and its injury in RLG/RPSG procurement. Unrecognizable on conventional three-dimensional (3-D) images, its significance is underestimated.We enrolled 500 patients who underwent preoperative imaging for scheduled surgeries at two major transplant centers. All-in-one 3-D images consisting of the hepatic artery, portal vein, and bile duct were constructed. Early bifurcation of the RHA and the RPHA was defined as the arteries bifurcating proximal to the cutting line of the right hepatic duct and the right posterior duct, respectively.Early bifurcation of the RHA was seen in 11.3% of cases of an infra-portal RPHA and in 46.0% of cases of a supra-portal RPHA (P0.001). Early bifurcation of the RPHA was encountered in 35.3% of cases of an infra-portal RPHA, in no cases of a supra-portal RPHA, and in 100% of cases in which the arteries to segment 6/7 arose individually from the RHA. The overall incidence of early bifurcation was 19.9% for RHA and 43.6% for RPHA.Early bifurcation of the RHA and the RPHA is frequently encountered and requires caution for RLG/RPSG procurement. Special attention should be paid to supra-portal RPHA for RLG procurement.

Backgrounds In the era of multidisciplinary treatment strategy, resectability for hepatocellular carcinoma (HCC) should be defined. This study aimed to propose and validate a resectability classification of HCC. Methods We proposed following the three groups; resectable-(R), borderline resectable-(BR), and unresectable (UR)-HCCs. Resectable two groups were sub-divided according to the value of indocyanine green clearance of remnant liver (ICG-Krem) and presence of macrovascular invasion (MVI); BR-HCC was defined as resectable HCCs with MVI and/or ICG-Krem≥0.03– Results A total of 361 patients were enrolled in the study. Of these, R-, BR- and UR-HCC were found in 251, 46, and 64 patients, respectively. In patients with resected HCC, ICG-Krem≥0.05 was associated with decreased risk of clinically relevant posthepatectomy liver failure (p=0.013) and the presence of MVI was associated with worse overall survival (OS) (pppp Conclusion Our proposal of resectability for HCC allows for stratifying survival outcomes of HCC and may help to determine treatment strategy.

In hepatectomy, the Pringle maneuver is commonly used, but its association with iatrogenic injury is not yet well understood. This report presents a case of dissecting aneurysm of the proper hepatic artery (PHA) possibly associated with the Pringle maneuver during laparoscopic hepatectomy, that was successfully treated by transcatheter arterial embolization (TAE). The patient was a woman in her 70s, and repeat hepatectomy for liver metastasis of rectal neuroendocrine neoplasm was planned. She underwent hand-assisted laparoscopic hepatectomy with the Pringle maneuver. On postoperative day (POD) 7, enhanced computed tomography showed a dissecting aneurysm of the PHA. TAE of the PHA to prevent hemorrhage was performed on POD 9 with no complications. Even after TAE, intrahepatic arterial flow was provided by the peribiliary arteries. This case suggests the possibility that the Pringle maneuver can cause a dissecting aneurysm of the hepatic artery.

Clinic-pathological findings of HCC patients.

Legends for supplemental Figure 1-3.

Supplemental Figure 3. Cancer stem cell properties of K19+ PLC/PRF/5 and Hep3B cells in vivo

Supplemental Table 1. Clinicopathological findings of HCC patients

Purpose: The current lack of tools for easy assessment of cancer stem cells (CSC) prevents the development of therapeutic strategies for hepatocellular carcinoma (HCC). We previously reported that keratin 19 (K19) is a novel HCC-CSC marker and that PET with 18F-fluorodeoxyglucose (18F-FDG) is an effective method for predicting postoperative outcome in hepatocellular carcinoma. Herein, we examined whether K19+ HCC-CSCs can be tracked using 18F-FDG-PET.Experimental Design: K19 and glucose transporter-1 (GLUT1) expression was evaluated by IHC in 98 hepatocellular carcinoma patients who underwent 18F-FDG-PET scans before primary tumor resection. Standardized uptake values (SUV) for primary tumors and tumor-to-nontumor SUV ratios (TNR) were calculated using FDG accumulation levels, and values were compared among K19+/K19− patients. Using hepatocellular carcinoma cell lines encoding with a K19 promoter–driven enhanced GFP, 18F-FDG uptake and GLUT1 expression were examined in FACS-isolated K19+/K19− cells.Results: In hepatocellular carcinoma patients, K19 expression was significantly correlated with GLUT1 expression and FDG accumulation. ROC analyses revealed that among preoperative clinical factors, TNR was the most sensitive indicator of K19 expression in hepatocellular carcinoma tumors. In hepatocellular carcinoma cells, FACS-isolated K19+ cells displayed significantly higher 18F-FDG uptake than K19− cells. Moreover, gain/loss-of-function experiments confirmed that K19 regulates 18F-FDG uptake through TGFβ/Smad signaling, including Sp1 and its downstream target GLUT1.Conclusions:18F-FDG-PET can be used to predict K19 expression in hepatocellular carcinoma and should thereby aid in the development of novel therapeutic strategies targeting K19+ HCC-CSCs. Clin Cancer Res; 23(6); 1450–60. ©2016 AACR.

Flow of the patients through the study.

Supplemental Table 2. Primer sequences for PCR, RT-PCR, qPCR, and qRT-PCR

Supplemental Figure Legends. The description of the Supplemental Figure 1-3

Supplemental Table 4. Univariate analysis with respect to outcome in the transplantation group

Gain/loss of K19 function in HCC cells.

Purpose: Keratin 19 (K19) is a known marker of poor prognosis and invasion in human hepatocellular carcinoma (HCC). However, the relationship between K19 and cancer stem cells (CSCs) is unclear. Here, we determined whether K19 can be used as a new CSC marker and therapeutic target in HCC.Experimental Design: HCC cell lines were transfected with a K19 promoter–driven enhanced green fluorescence protein gene. CSC characteristics, epithelial–mesenchymal transition (EMT), and TGFb/Smad signaling were examined in FACS-isolated K19+/K19− cells. K19 and TGFb receptor 1 (TGFbR1) expression in 166 consecutive human HCC surgical specimens was examined immunohistochemically.Results: FACS-isolated single K19+ cells showed self-renewal and differentiation into K19− cells, whereas single K19− cells did not produce K19+ cells. K19+ cells displayed high proliferation capacity and 5-fluorouracil resistance in vitro. Xenotransplantation into immunodeficient mice revealed that K19+ cells reproduced, differentiated into K19− cells, and generated large tumors at a high frequency in vivo. K19+ cells were found to be involved in EMT and the activation of TGFb/Smad signaling, and these properties were suppressed by K19 knockdown or treatment with a TGFbR1 inhibitor. The TGFbR1 inhibitor also showed high therapeutic effect against K19+ tumor in the mouse xenograft model. Immunohistochemistry of HCC specimens showed that compared with K19− patients, K19+ patients had significantly poorer recurrence-free survival and higher tumor TGFbR1 expression.Conclusions: K19 is a new CSC marker associated with EMT and TGFb/Smad signaling, and it would thus be a good therapeutic target for TGFbR1 inhibition. Clin Cancer Res; 21(13); 3081–91. ©2015 AACR.

Primer sequences for RT-PCR and qRT-PCR.

Univariate analysis with respect to outcome.

Supplemental Table 3. Univariate analysis with respect to outcome in the resection group

EGFP-marking of the K19+ cells in human HCC cell lines.

Although the number of minimally invasive liver resections (MILRs) has been steadily increasing in many institutions, minimally invasive anatomic liver resection (MIALR) remains a complicated procedure that has not been standardized. We present the results of a survey among expert liver surgeons as a benchmark for standardizing MIALR.We administered this survey to 34 expert liver surgeons who routinely perform MIALR. The survey contained questions on personal experience with liver resection, inflow/outflow control methods, and identification techniques of intersegmental/sectional planes (IPs).All 34 participants completed the survey; 24 experts (70%) had more than 11 years of experience with MILR, and over 80% of experts had performed over 100 open resections and MILRs each. Regarding the methods used for laparoscopic or robotic anatomic resection, the Glissonean approach (GA) was a more frequent procedure than the hilar approach (HA). Although hepatic veins were considered essential landmarks, the exposure methods varied. The top three techniques that the experts recommended for identifying IPs were creating a demarcation line, indocyanine green negative staining method, and intraoperative ultrasound.Minimally invasive anatomic liver resection remains a challenging procedure; however, a certain degree of consensus exists among expert liver surgeons.

Background In laparoscopic anatomic liver resection, an increasingly common procedure, the hepatic vein-guided approach is widely used although the hepatic vein tributaries can be a major source of bleeding in the event of inadvertent injury. This report describes the anatomy of the middle hepatic vein (MHV) including its tributaries based on reconstructed three-dimensional computed tomography images and provides anatomic data to enable safe middle hepatic vein-guided liver resection. Methods Following simulation modeling of the hepatic vasculatures, reconstructed MHV data was pooled from 35 healthy liver donors. Yields of the MHV tributaries were analyzed to enable MHV-guided liver resection. Results A total of 252 tributaries were identified in the 35 donors. The MHV yielded fewer tributaries from its anterior and posterior aspects than from its right-side and left-side aspects (40 [15.9%], 13 [5.2%], 93 [36.9%], and 106 [42.1%], respectively). The MHV tributaries from the anterior and posterior aspects were smaller in diameter than those from the right-side and left-side aspects (median, 3.0, 2.0, 4.8, and 4.0 mm, respectively). Discussion Our simulation revealed that MHV dissection from the anterior or posterior aspect poses a lower risk of injury to the MHV tributaries compared to dissection from either lateral aspect. In addition, MHV dissection from the anterior or posterior aspect allows for safer identification and isolation of the thick MHV tributaries originating from the lateral aspects. Ideally, the anterior or posterior aspect of the MHV should be accessed and exposed before the lateral aspects are dissected to minimize the risk of MHV tributary injury.

This study aimed to assess an oncologic setting where patients with hepatocellular carcinoma (HCC) could benefit from liver resection (LR) compared to living donor liver transplantation (LDLT) using 18F-fluorodeoxyglucose (FDG) positron emission tomography. The consecutive data of patients with HCC who underwent 18F-FDG PET before LR (LR group, n = 314) and LDLT (LDLT group, n = 65) between 2003 and 2015 were retrospectively analyzed. Tumor 18F-FDG avidity was quantified as the tumor to liver standardized uptake value ratio (TLR, cut-off value was defined at 2). Multivariate analysis was performed to assess significant preoperative tumor factors in the LR group. Survival outcomes between the two groups were stratified by these factors. The 5-year overall survival (OS: 56.9% vs. 73.8%, LR vs. LDLT, p

Background The aim of this study was to establish a quantitative equation to predict microvascular invasion (MVI) for patients with resectable hepatocellular carcinoma (HCC). Methods This retrospective study included 219 patients with resected HCC from 2004 to 2015. All had available three pre-operative serological markers (alfa-feto protein (AFP), fucosylated AFP (AFP-L3), and des-gamma-carboxy prothrombin (DCP)), and one imaging marker (tumor to liver ratio of SUVmax (TLR) by 18F-FDG-PET). A multiple linear regression model for predicting MVI was developed (2004–2009, n = 111) and then validated (2010–2015, n = 108). Further, impact on the obtained model on survival outcomes was assessed. Results Using the derivation cohort, following equation was developed; MVI probability (%) = 14.2 × log10DCP + 9.9 × TLR - 22.0. This model resulted in an area under receiver operating characteristic curve (ROC) of 0.806 and 0.751, in the derivation and validation cohort, respectively. Furthermore, MVI probability ≥40% determined by ROC analysis was associated with worse overall survival and recurrence-free survival in the derivation and the validation cohort (all p Conclusion A quantitative model, using DCP and TLR, was able to preoperatively predict with good performance MVI and long-term outcomes in patients with HCC after liver resection.

Several studies have suggested that laparoscopic liver resection (LLR) is associated with fewer postoperative complications than open liver resection (OLR) for hepatocellular carcinoma (HCC). However, this issue remains controversial since the data may have been attributable to an imbalance in patients’ background. We retrospectively analyzed 290 hepatectomies for HCC undertaken between 2011 and 2019. Liver resection difficulty was based on the 3 levels of the Institut Mutualiste Montsouris classification. Resection ratio was calculated using computed tomography volumetry. Patient characteristics were compared between the LLR and OLR groups. Propensity score matching (PSM) was adopted to adjust the imbalance between the cohorts, and the incidence of postoperative complications was compared. The difficulty and resection ratio were significantly lower in LLR (n = 112) than in OLR (n = 178) (difficulty grade I/II/III: 84/10/18 vs. 43/39/96, p

Although decreased antithrombin-III (AT-III) is a risk factor for portal vein thrombosis (PVT) in patients with liver cirrhosis, the association between postoperative PVT and postoperative AT-III levels is unknown in patients undergoing hepatectomy. Patients who underwent hepatectomy between 2015 and 2018 were retrospectively analyzed. Postoperative PVT was assessed on CT at days 6–9 after hepatectomy. One-to-one propensity score (PS) matching was used to match the baseline characteristics. Of the 295 patients included in this analysis, 19 patients (6.4%) were diagnosed with postoperative PVT. The AT-III level on postoperative day (POD) 3 predicted postoperative PVT with a sensitivity/specificity of 74%/59% (AUC, 0.644; cut-off value, 60%; p = 0.032). Multivariate analysis revealed that AT-III levels ≤ 60% on POD3 (OR, 3.01; 95% CI 1.02–8.89; p = 0.046), cirrhosis (OR, 5.88; 95% CI 1.92–18.0; p = 0.002) and right-sided hepatectomy (OR, 4.16; 95% CI 1.45–11.9; p = 0.0079) were significant risk factors for postoperative PVT. After PS matching, 56 patients with and without AT-III supplementation were analyzed. The two groups had a similar incidence of PVT (p = 0.489). Patients with AT-III levels ≤ 60% on POD3 should be carefully followed up regarding postoperative PVT. Our results did not support the efficacy of routine AT-III supplementation for the prophylaxis of postoperative PVT.

Purpose In this systematic review, we aimed to clarify the useful anatomic structures and assess available surgical techniques and strategies required to safely perform minimally invasive anatomic liver resection (MIALR), with a particular focus on the hepatic veins (HVs). Methods A systematic review was conducted using MEDLINE/PubMed for English articles and Ichushi databases for Japanese articles through September 2020. The quality assessment of the articles was performed in accordance with the Scottish Intercollegiate Guidelines Network (SIGN). Results A total of 3,372 studies were obtained, and 59 were selected and reviewed. Due to the limited number of published comparative studies and case series, the degree of evidence from our review was low. Thirty-two articles examined the anatomic landmarks and crucial structures for approaching HVs. Regarding the direction of HV exposure, 32 articles focused on the techniques and advantages of exposing HVs from either the root or the periphery. Ten articles focused on the techniques to perform a segmentectomy 8 in particularly difficult cases of MIALR. In seven articles, bleeding control from HVs was also discussed. Conclusions This review may help experts reach a consensus regarding the best approach to the management of hepatic veins during MIALR.

Background In preparation for the upcoming consensus meeting in Tokyo in 2021, this systematic review aimed to analyze the current available evidence regarding surgical anatomy of the liver, focusing on useful landmarks, strategies and technical tools to perform precise anatomic liver resection (ALR). Methods A systematic review was conducted on MEDLINE/PubMed for English articles and on Ichushi database for Japanese articles until September 2020. The quality assessment of the articles was performed in accordance with the Scottish Intercollegiate Guidelines Network (SIGN). Results A total of 3169 manuscripts were obtained, 1993 in English and 1176 in Japanese literature. Subsequently, 63 English and 20 Japanese articles were selected and reviewed. The quality assessment of comparative series and case series was revealed to be usually low; only six articles were qualified as high quality. Forty-two articles focused on analyzing intersegmental/sectional planes and their relationship with specific hepatic landmark veins. In 12 articles, the authors aimed to investigate liver surface anatomic structures, while 36 articles aimed to study technological tools and contrast agents for surgical segmentation during ALR. Although Couinaud's classification has remained the cornerstone in daily diagnostic/surgical practices, it does not always portray the realistic liver segmentation and there has been no standardization on which a single strategy should be followed to perform precise ALR. Conclusions A global consensus should be pursued in order to establish clear guidelines and proper recommendations to perform ALR in the era of minimally invasive surgery.

Highlights • Combined hepatocellular-cholangiocarcinoma (cHCC-CCA) is a rare primary liver carcinoma. • The indications for live transplantation for cHCC-CCA remain controversial. • In this case series, patients who met the Milan criteria on the pathological examination had good prognosis. • By itself, cHCC-CCA was not a contraindication for liver transplantation., Introduction Combined hepatocellular-cholangiocarcinoma (cHCC-CCA) is a rare primary liver carcinoma whose components include both hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA). Indications for liver transplantation for cHCC-CCA remain controversial. Case presentations Four patients underwent living donor liver transplantation (LDLT) for cHCC-CCA. All patients had multiple tumor nodules preoperatively diagnosed as HCC. Postoperative pathological examinations revealed that one of the tumors was cHCC-CCA. Cases 1 and 2 underwent LDLT for cirrhosis with HCC tumors that met Milan criteria. Case 3 underwent LDLT for recurrent HCC tumors with nonalcoholic steatohepatitis. Although the preoperative examinations showed that the patient met the Kyoto, but not Milan criteria, postoperative pathological examinations revealed that the patient did meet Milan criteria. The three patients who met Milan criteria on postoperative pathological examination had no recurrences after LDLT. Case 4 had multiple tumors with alcoholic liver cirrhosis. Although the preoperative examinations showed that the patient did not meet Milan criteria—but did meet Kyoto criteria—, on postoperative pathological examinations, the patient met neither Millan nor Kyoto criteria. He died of tumor recurrence 15 months after LDLT. Discussion and conclusions Our experiences suggested that patients who meet Millan or Kyoto criteria experienced acceptable outcomes of LDLT for cHCC-CCA. By itself, cHCC-CCA is not contraindication for liver transplantation.

Liver resection is a standard therapy for colorectal liver metastasis. However, the impact of anatomical resection and nonanatomical resection on the survival in patients with Kirsten rat sarcoma-wild-type and Kirsten rat sarcoma-mutated colorectal liver metastasis remain unclear. We investigated whether anatomical resection versus nonanatomical resection improves survival in colorectal liver metastasis stratified by Kirsten rat sarcoma mutational status.Among 639 consecutive patients with colorectal liver metastasis who underwent primary liver resection between January 2008 and December 2017, 349 patients were excluded due to their unknown Kirsten rat sarcoma mutational status, or due to receiving anatomical resection with concomitant non-anatomical resection, radiofrequency, or R2 resection. Accordingly, 290 patients with colorectal liver metastasis were retrospectively assessed. The relationships between resection types and survival were investigated in Kirsten rat sarcoma-wild-type and -mutated groups.Anatomical resection was performed in 77/186 (41%) and 44/104 (42%) patients with Kirsten rat sarcoma-wild-type and Kirsten rat sarcoma-mutated genetic statuses, respectively. For both, the clinical-pathologic factors were comparable, except a larger maximum tumor size and surgical margin were observed in anatomical resection cases. Anatomical resection patients had significantly longer recurrence-free survival and overall survival than nonanatomical resection cases in the Kirsten rat sarcoma-wild-type group (recurrence-free survival, P.001; overall survival, P = .005). No significant recurrence-free survival or overall survival differences were observed between Kirsten rat sarcoma-mutated anatomical resection and non-anatomical resection (recurrence-free survival, P = .132; overall survival, P = .563). Although, intrahepatic recurrence in Kirsten rat sarcoma-wild-type and -mutated colorectal liver metastasis was comparable (P = .973), extrahepatic recurrence was increased in Kirsten rat sarcoma-mutated versus -wild-type colorectal liver metastasis (P.001).In contrast to Kirsten rat sarcoma-mutated colorectal liver metastasis with higher extrahepatic recurrence after liver resection, local liver control via anatomical resection improved the postoperative survival in patients with Kirsten rat sarcoma-wild-type colorectal liver metastasis.

Objective Evaluating the perioperative outcomes of minimally invasive (MIV) donor hepatectomy for adult live donor liver transplants in a large multi-institutional series from both Eastern and Western centers. Background Laparoscopic liver resection has become standard practice for minor resections in selected patients in whom it provides reduced postoperative morbidity and faster rehabilitation. Laparoscopic approaches in living donor hepatectomy for transplantation, however, remain controversial because of safety concerns. Following the recommendation of the Jury of the Morioka consensus conference to address this, a retrospective study was designed to assess the early postoperative outcomes after laparoscopic donor hepatectomy. The collective experience of 10 mature transplant teams from Eastern and Western countries was reviewed. Methods All centers provided data from prospectively maintained databases. Only left and right hepatectomies performed using a MIV technique were included in this study. Primary outcome was the occurrence of complications using the Clavien-Dindo graded classification and the Comprehensive Complication Index during the first 3 months. Logistic regression analysis was used to identify risk factors for complications. Results In all, 412 MIV donor hepatectomies were recorded including 164 left and 248 right hepatectomies. Surgical technique was either pure laparoscopy in 175 cases or hybrid approach in 237. Conversion into standard laparotomy was necessary in 17 donors (4.1%). None of the donors died. Also, 108 experienced 121 complications including 9.4% of severe (Clavien-Dindo 3-4) complications. Median Comprehensive Complication Index was 5.2. Conclusions This study shows favorable early postoperative outcomes in more than 400 MIV donor hepatectomy from 10 experienced centers. These results are comparable to those of benchmarking series of open standard donor hepatectomy.

The Brisbane 2000 Terminology for Liver Anatomy and Resections, based on Couinaud's segments, did not address how to identify segmental borders and anatomic territories of less than one segment. Smaller anatomic resections including segmentectomies and subsegmentectomies, have not been well defined. The advent of minimally invasive liver resection has enhanced the possibilities of more precise resection due to a magnified view and reduced bleeding, and minimally invasive anatomic liver resection (MIALR) is becoming popular gradually. Therefore, there is a need for updating the Brisbane 2000 system, including anatomic segmentectomy or less. An online "Expert Consensus Meeting: Precision Anatomy for Minimally Invasive HBP Surgery (PAM-HBP Surgery Consensus)" was hosted on February 23, 2021.The Steering Committee invited 34 international experts from around the world. The Expert Committee (EC) selected 12 questions and two future research topics in the terminology session. The EC created seven tentative definitions and five recommendations based on the experts' opinions and the literature review performed by the Research Committee. Two Delphi Rounds finalized those definitions and recommendations.This paper presents seven definitions and five recommendations regarding anatomic segmentectomy or less. In addition, two future research topics are discussed.The PAM-HBP Surgery Consensus has presented the Tokyo 2020 Terminology for Liver Anatomy and Resections. The terminology has added definitions of liver anatomy and resections that were not defined in the Brisbane 2000 system.

Background The concept of Minimally invasive anatomic liver resection (MIALR) is gaining popularity. However, specific technical skills need to be acquired to safely perform MIALR. The "Expert Consensus Meeting: Precision Anatomy for Minimally Invasive HBP Surgery (PAM-HBP Surgery Consensus)" was developed as a special program during the 32nd meeting of the Japanese Society of Hepato-Biliary-Pancreatic Surgery (JSHBPS). Methods Thirty-four international experts gathered online for the consensus. A Research Committee performed a comprehensive literature review, classifying studies according to the Scottish Intercollegiate Guidelines Network (SIGN) method. Based on the literature review and experts' opinions, tentative recommendations were drafted and circulated among experts using online Delphi Rounds. Finally, formulated recommendations were presented online in the Expert Consensus Meeting of the JSHBPS on February 23rd, 2021. The final recommendations were validated and finalized by the 2nd Delphi Round in May 2021. Results Seven Clinical Questions (CQs) were selected, and 22 recommendations were formulated. All recommendations reached more than 85% consensus among experts at the final Delphi Round. Conclusions The Expert Consensus Meeting for safely performing MIALR has presented a set of clinical guidelines based on available literature and experts' opinions. We expect these guidelines to have a favorable effect on the safe implementation and development of MIALR.