The history of PRETEXT explains both its power and its problems. Before 1990, there was no common language for staging malignant liver tumors in children; the extent of disease was judged from what surgeons found in the operating room or from the resected specimen afterward. A joint working group spanning the International Society of Pediatric Oncology, the German Pediatric Oncology Group, the Japanese Liver study, and Canadian representatives agreed in 1992 to adopt the imaging-based grouping system first used in the SIOPEL 1 trial as a global standard. Crucially, this shift to pretreatment imaging meant that children too sick for immediate surgery could finally be included in trials. The system was revised in 2005 and again in 2017, when a new set of definitions was crafted to serve the Paediatric Hepatic International Tumor Trial, the largest collaborative effort yet undertaken against these rare cancers.

The modern system has two components. The PRETEXT group, from I to IV, reflects how many contiguous liver sections are free of tumor, with the liver divided into left lateral, left medial, right anterior, and right posterior sections using hepatic and portal venous anatomy as landmarks. Involvement of the caudate lobe, segment I, is by convention classified as at least PRETEXT II. Alongside the group sit eight annotation factors, memorably summarized as VPEFRCNM: venous involvement, portal vein involvement, extrahepatic extension, multifocality, tumor rupture, caudate lobe involvement, lymph node involvement, and distant metastases. Each is recorded as simply present or absent. After neoadjuvant chemotherapy, the same framework is reapplied and called POSTTEXT. The whole edifice feeds directly into the CHIC risk-stratification scheme that determines whether a child receives standard, intermediate, or high-risk chemotherapy.

The first major weakness, the authors argue, lies upstream of interpretation entirely: image acquisition. Staging requires multiplanar, multiphase, high-quality MRI or CT, but imaging small children is notoriously difficult. Motion artifacts plague upper abdominal scans in young patients, small body volumes demand high spatial resolution, and sedation or general anesthesia adds risk and complexity. Consensus imaging guidelines from the American College of Radiology’s Pediatric LI-RADS Working Group have helped, but the SIOPEL group reports that implementation and adherence vary considerably across Europe. A recent study of 358 CT scans and 144 MRI scans from 105 institutions in 226 patients, part of the Children’s Oncology Group AHEP0731 study, documented considerable heterogeneity even within the United States. In Europe, marked variation persists, with significant ongoing use of CT despite guideline recommendations favoring MRI, reflecting differences in expertise, resources, scanner technology, and access to appropriate contrast agents. Notably, the European Society of Paediatric Radiology has yet to publish dedicated guidance on pediatric liver imaging.

Then comes the problem of human disagreement. The system’s binary nature, with sections and annotation factors marked only as involved or uninvolved, leaves little room for nuance when tumors push against boundaries or ambiguously abut blood vessels. Studies comparing PRETEXT assignments between local and central radiologists have found kappa values of 0.57 to 0.79, indicating moderate to substantial agreement, and there has been no apparent improvement over time despite better scanners and formal imaging recommendations. Agreement appears higher for POSTTEXT, with kappa values of 0.82 and 0.93 in two contemporary studies, but annotation factors remain the weak point. Hepatic venous involvement shows the lowest inter-observer agreement of all, and local radiologists have reported particularly high false-positive rates for vascular involvement, extrahepatic extension, rupture, and lymph node involvement. Rarity compounds the problem: hepatoblastoma strikes only about 1.5 children per million per year, so many hospitals encounter these tumors too infrequently to build deep expertise. Even within the SIOPEL Radiology Group itself, a 2024 survey found many members struggled with the system.

Some of the deepest difficulties are anatomical rather than technical. PRETEXT boundaries are theoretical planes that are hard to delineate in practice, especially when large tumors distort the liver. The boundary between the left medial and right anterior sections, Cantlie’s line, runs from the middle hepatic vein to the middle of the gallbladder fossa, but a bulky tumor can deform the plane while the landmarks stay put, making it genuinely hard to distinguish true invasion from mere mass effect. Small interpretive differences can flip a child from PRETEXT II to III and change management entirely. The consequences are measurable: one study comparing imaging-based PRETEXT with pathology found the stage correct in only 51 percent of cases, over-staged in 37 percent, and under-staged in 12 percent. The high over-staging rate partly reflects an official recommendation to assign the highest group when uncertain, a rule that trades surgical conservatism for statistical noise.

Vascular assessment exposes perhaps the sharpest mismatch between the staging system and modern surgery. Tumor proximity to the hepatic veins, portal vein, and inferior vena cava determines whether a tumor can be resected or whether transplantation is needed, yet V and P status alone do not capture resectability. A PRETEXT I or II tumor that abuts the portal vein bifurcation by less than 180 degrees is technically P-negative but may still require an extreme resection or a transplant. Conversely, tumor thrombus extending into the contralateral portal vein or the draining veins of unaffected sections renders the whole liver effectively involved, leading surgeons to treat such tumors as functionally PRETEXT IV even when the group assignment says otherwise. The system also ignores details that matter enormously in the operating room, such as thrombus extension into the superior mesenteric vein, which can necessitate combined liver and small bowel transplantation, or tumor emboli that travel into the pulmonary arteries, which the authors suggest reporting separately as embolic M-positive disease.

The annotation factors each carry their own traps. Extrahepatic spread occurs in fewer than 5 percent of children at diagnosis but carries a poor prognosis, and distinguishing contiguous invasion from simple proximity or reactive inflammation remains a diagnostic challenge; targeted ultrasound can help by showing whether tumor and adjacent organs move together or freely. Rupture is defined narrowly as free intraperitoneal fluid with evidence of tumor-associated hemorrhage, excluding contained subcapsular ruptures that still demand altered biopsy and surgical planning. Multifocality, present in up to 20 percent of hepatoblastoma cases, can emerge or vanish between PRETEXT and POSTTEXT as chemotherapy shrinks tumors and separates confluent foci, yet sites of disease that become radiologically occult may still harbor viable microscopic tumor and remain critical for curative surgery. Lymph node assessment relies on size and morphology criteria that are imperfect in both directions, and lung metastasis assessment is hampered by the fact that up to two-thirds of resected suspected pulmonary metastases in these children prove benign.

POSTTEXT, the post-treatment counterpart, inherits every one of these problems and adds its own. Imaging cannot reliably indicate tumor viability, so apparent abnormalities may not correspond to residual disease, while occult tumor can persist where images look clean. Current risk stratification and treatment allocation still rest on the initial PRETEXT, and the role of POSTTEXT in guiding decisions or predicting outcomes has not been established. This creates a troubling possibility the authors highlight: children whose tumors show marked radiological downstaging may still undergo resections planned according to the original tumor distribution, exposing them to more extensive surgery, and more morbidity, than strictly necessary to control their disease.

The paper closes with a program of remedies. The SIOPEL group proposes standardized imaging protocols, structured reporting templates that explicitly document uncertainty and surgery-specific details such as future liver remnant volume, routine multidisciplinary tumor board discussion, double and central review for complex cases, and a secure cloud-based platform for consensus review and training. They call for validation studies quantifying inter-observer agreement under standardized protocols, refinement of ambiguous definitions such as vascular encasement thresholds, and eventual inclusion of radiology-specific research questions in trial protocols. Emerging tools, from improved MRI sequences that enable free-breathing imaging to AI-based segmentation and deep learning methods, may help, though the authors caution that robust pediatric evidence remains limited. No formal revision of PRETEXT is currently planned, and any such effort would require global consensus on its primary aims. Until then, the message to the worldwide pediatric oncology community is clear: the system that has unified childhood liver cancer staging since 1990 still works, but only if everyone using it understands exactly where it bends.

Subject of Research: Limitations of the PRETEXT imaging staging system for pediatric malignant liver tumors

Article Title: Challenges with the PRETEXT staging system: a SIOPEL Radiology Group position paper

Article References: Lohne, S. M. H., Hebelka, H., Prince, J. F., Bohte, A. E., Littooij, A. S., de Lange, C., Deganello, A., Costa Dias, S., Chambers, G., Toso, S., Habre, C., Pace, E., Franchi-Abella, S., Woodley, H., & McGuirk, S. P. (2026). Challenges with the PRETEXT staging system: a SIOPEL Radiology Group position paper. Pediatric Radiology. https://doi.org/10.1007/s00247-026-06786-w

Image Credits: AI Generated

DOI: 10.1007/s00247-026-06786-w

Keywords: PRETEXT, hepatoblastoma, pediatric liver tumors, radiology, cancer staging, SIOPEL, MRI, POSTTEXT, risk stratification, liver transplantation, inter-observer variability, structured reporting

Recently, a multi-institutional consortium led by scientists at Baylor College of Medicine and Texas Children’s Hospital, in conjunction with several global collaborators, has embarked on a rigorous exploration of HBC tumors. Their work, published in the Journal of Hepatology, leverages advanced molecular profiling technologies to dissect the cellular architecture of these tumors at unprecedented resolution. By applying sophisticated single-cell DNA and RNA sequencing methodologies, the team was able to catalog individual tumor cells’ genomic and transcriptomic identities, thereby illuminating the dynamic cellular heterogeneity within HBC.

Single-cell sequencing revealed a remarkable discovery: HBC tumors encompass a triad of distinct cancer cell populations. These include cells resembling classic hepatoblastoma, others mirroring hepatocellular carcinoma, and a unique class of HBC-specific cells that simultaneously express molecular hallmarks of both tumor types. This underscores the remarkable plasticity and complex developmental origins of HBC cancers, distinguishing them from their HB and HCC counterparts, which traditionally have been seen as separate biological entities.

Further analyses demonstrated that HBC tumors originate from hepatic stem cells, a primitive cell population responsible for liver regeneration and development. These stem-like tumor cells exhibit differentiation arrest, implying they do not mature into fully differentiated hepatocytes. This arrested differentiation imparts an intrinsic resistance to conventional chemotherapy and immunotherapy regimens, thereby explaining the poorer clinical outcomes observed in children diagnosed with HBC compared to those with pure hepatoblastoma.

Clinical outcome data from 41 pediatric patients provided sobering evidence of this aggressive disease course. The five-year overall survival rate for children with typical hepatoblastoma stood at approximately 80%, whereas it was markedly lower, near 40%, for those with HBC tumors. Interestingly, patients who underwent liver transplantation showed improved survival, suggesting that surgical intervention may partly overcome the tumor’s chemoresistance.

Delving deeper into the molecular relationships among the diverse tumor cell types within HBC masses, the researchers uncovered evidence of cellular transitions along a developmental continuum. Cells appear capable of transitioning from HB progenitors to intermediate HBC states and eventually to HCC-like phenotypes. This fluidity points to a spectrum of tumor evolution rather than discrete tumor classes, challenging traditional diagnostic frameworks.

Central to this tumor plasticity is the aberrant activation of the WNT signaling pathway, a critical regulator during early liver organogenesis. Typically, this pathway orchestrates hepatic stem cell proliferation and early differentiation but is tightly downregulated to permit maturation into functional hepatocytes. In HBC tumors, however, dysregulated WNT signaling remains persistently active, perpetuating the undifferentiated state of tumor cells and preventing their normal developmental progression.

The researchers experimentally modulated the WNT signaling cascade in HBC tumor models and found that inhibiting this pathway induced cellular differentiation and heightened sensitivity to chemotherapeutic agents. This notable finding positions WNT pathway components as promising therapeutic targets for overcoming treatment resistance in these tumors, advocating for the incorporation of pathway inhibitors into future clinical strategies.

The study further revealed that HBC tumors arise not from a single clonal progenitor but rather from multiple independent hepatoblastoma cells that simultaneously undergo transitions to carcinoma-like states. This polyclonal origin introduces additional complexity to the tumor microenvironment and suggests diverse evolutionary trajectories within individual tumors.

Collectively, these groundbreaking insights culminate in a novel developmental model for pediatric liver cancer, hypothesizing that sustained WNT pathway activation during early liver development engenders tumor heterogeneity by impeding differentiation and fostering asynchronous transitions from HB to HBC to HCC. This model not only refines our understanding of tumor biology but also provides a conceptual framework for therapeutic innovation.

The implications of the work extend beyond liver cancer, illustrating how dysregulated developmental signaling pathways can engender complex tumor phenotypes and influence clinical outcomes. This underscores the necessity of precision medicine approaches tailored to the unique cellular and molecular context of each tumor subtype to improve survival and quality of life for affected children.

The advancement in characterizing the cellular atlas of HBC tumors lays a foundation for future inquiries into targeted therapeutics and diagnostic markers. Ongoing research will likely explore combinatorial treatments aimed at modulating differentiation and immune responsiveness, potentially transforming the grim prognosis historically associated with high-risk pediatric liver cancers.

This transformative study, supported by generous funding from the European Union Horizon 2020, the Cancer Prevention and Research Institute of Texas, the National Institutes of Health, and others, represents a beacon of hope illuminating the path toward deeper biological understanding and improved clinical management of pediatric liver cancers.

Subject of Research: Human tissue samples

Article Title: Asynchronous Transitions from High-Risk Hepatoblastoma to Carcinoma

News Publication Date: 28-Feb-2026

Web References:

• Journal of Hepatology: https://doi.org/10.1016/j.jhep.2026.02.023
• Previous identification of HBC: https://www.journal-of-hepatology.eu/article/S0168-8278(22)00275-6/fulltext

References:
Sumazin, P. et al. (2026). Asynchronous Transitions from High-Risk Hepatoblastoma to Carcinoma. Journal of Hepatology. https://doi.org/10.1016/j.jhep.2026.02.023

Keywords: Pediatric liver cancer, hepatoblastoma, hepatocellular carcinoma, hepatoblastoma with carcinoma features, tumor heterogeneity, WNT signaling pathway, single-cell sequencing, tumor differentiation, liver development, chemotherapy resistance, liver transplantation, tumor evolution

Hepatoblastoma’s rapid proliferation is intricately linked to the Warburg effect, a metabolic hallmark characterized by enhanced glycolysis even under aerobic conditions. This altered glucose metabolism supports not only tumor growth but also contributes to the creation of a microenvironment conducive to malignancy. By mining gene expression databases such as GEO, the researchers identified SKP2 as being notably upregulated in HB tissues compared to non-cancerous liver samples. They confirmed this elevated expression in patient-derived biopsies, underscoring the clinical relevance of their findings and positioning SKP2 as a candidate biomarker for HB.

Functionally, SKP2 is well-known for its role in cell cycle regulation through targeting various cell cycle inhibitors for ubiquitin-mediated degradation. However, this study pioneers insights into its non-canonical roles by demonstrating how SKP2 directs the ubiquitination of IDH1, an enzyme critical for cellular metabolism. Through co-immunoprecipitation assays, the team unequivocally established the physical and functional interaction between SKP2 and IDH1 within HB cells, suggesting a direct regulatory axis that links proteostasis with metabolic reprogramming.

The use of well-established HB cell lines, including HepG2 and Huh6, allowed for controlled in vitro experimentation. Here, modulation of SKP2 levels revealed pronounced effects not just on cell proliferation but also on migratory and invasive capabilities of tumor cells. These phenotypic changes were tightly correlated with disruptions in glucose metabolism, as monitored via ELISA, flow cytometry, and confocal microscopy techniques. The convergence of these methodologies provided compelling evidence that SKP2’s impact extends beyond mere cell cycle control to extensively remodeling tumor bioenergetics through IDH1.

A particularly innovative aspect of the investigation was the application of IDH1 inhibitors in SKP2-suppressed hepatoblastoma models. The results showed that dampening IDH1 activity could counteract the tumor-suppressive effects triggered by the inhibition of SKP2. This finding illuminates the therapeutic potential of combinatorial targeting, wherein simultaneous modulation of SKP2 and IDH1 pathways may synergistically impede tumor progression. It also emphasizes the intricate feedback loops that sustain HB oncogenesis, which may be exploited to overcome resistance mechanisms inherent to monotherapies.

On a mechanistic level, the ubiquitylation of IDH1 by SKP2 appears to stabilize IDH1 protein accumulation rather than marking it for proteasomal degradation, a deviation from classical ubiquitin signaling pathways. This stabilization could enhance the enzymatic activity of IDH1, thereby promoting alterations in the tricarboxylic acid (TCA) cycle and associated metabolic fluxes. This nuanced modification suggests that ubiquitination does not solely serve as a degradation signal in this context but acts as a finely tuned regulator of metabolic enzymes, thereby linking ubiquitin biology with metabolic reprogramming in cancer.

The implications of these findings reach far into clinical oncology. Elevated SKP2 expression correlates strongly with poorer prognoses in HB patients, implicating it as a formidable driver of malignancy. The demonstration that SKP2 modulates not only proliferative capacity but also glucose metabolism via ubiquitin-mediated regulation of IDH1 offers a dual therapeutic angle that could be exploited for more effective interventions. Targeting SKP2 or its downstream metabolic effectors may disrupt the tumor’s energy supply and cell cycle progression simultaneously, delivering a potent anti-cancer strategy.

Moreover, animal models bearing HB tumors were employed to validate the in vitro results, enriching the translational value of the study. Tumor-bearing mice treated with SKP2 inhibitors exhibited significant decreases in tumor growth and metabolic activity, reinforcing the therapeutic promise of SKP2 blockade. This in vivo evidence is critical for establishing the feasibility of moving SKP2-targeting drugs into clinical testing phases, especially for children suffering from this aggressive disease.

The study also sparks new questions regarding the broader role of SKP2 and ubiquitin signaling in cancer metabolism. Given that IDH1 mutations are frequently implicated in other malignancies like gliomas and acute myeloid leukemia, understanding how SKP2-mediated ubiquitination affects mutant versus wild-type IDH1 could have broader oncological relevance. This line of inquiry may uncover universal therapeutic paradigms that transcend tumor types and metabolic contexts.

Importantly, the researchers employed an integrative approach combining bioinformatics, molecular biology, and advanced imaging to dissect the interplay between SKP2 and IDH1. This multidisciplinary methodology exemplifies how contemporary cancer research can unravel complex regulatory networks by leveraging the strength of diverse technologies. It sets a precedent for future studies aiming to bridge cell cycle machinery with metabolism in tumorigenesis.

Patient stratification based on SKP2 and IDH1 expression levels could further refine prognosis and treatment selection. By identifying subsets of HB patients with high SKP2 and IDH1 activity, clinicians might anticipate more aggressive disease courses and tailor therapies accordingly. This precision medicine approach ultimately aspires to improve survival rates and quality of life for pediatric patients challenged by hepatoblastoma.

Another facet worth exploring is the impact of SKP2-IDH1 regulation on the tumor microenvironment. Altered glucose metabolism often leads to acidification and immunosuppression within tumors, facilitating immune evasion. If SKP2 influences IDH1-driven metabolic flux, it may indirectly modulate immune cell infiltration and function, opening avenues for immunotherapy combinations.

The discovery that SKP2’s oncogenic capabilities extend beyond canonical degradation of cell cycle inhibitors to metabolic enzyme modulation redefines the protein as a master regulator of malignancy in hepatoblastoma. Targeting this multifaceted molecule could thus dismantle the tumor’s proliferative and metabolic underpinnings concurrently, offering a powerful therapeutic strategy that demands immediate attention in cancer research circles.

In summary, this seminal work elevates SKP2 to the forefront of hepatoblastoma research by illuminating its role as a critical modulator of cancer cell metabolism and cycle progression through the ubiquitin-mediated regulation of IDH1. The convergence of cellular signaling, post-translational modification, and metabolic rewiring underscores the complexity of cancer biology and the necessity for integrated therapeutic interventions.

As the scientific community digests these findings, clinical trials evaluating SKP2 and IDH1 inhibitors, alone or in combination, may become a focal point for advancing hepatoblastoma treatment. This study not only provides a mechanistic blueprint of tumor progression but also inspires optimism for children and families affected by this devastating disease.

Subject of Research: The study investigates the molecular role of SKP2-mediated ubiquitination of IDH1 in regulating the cell cycle and glucose metabolism within hepatoblastoma, the predominant pediatric liver cancer.

Article Title: SKP2 ubiquitylation modifies IDH1 to regulate hepatoblastoma cell cycle and glucose metabolism

Article References:
Yu, P., Li, J., Feng, W. et al. SKP2 ubiquitylation modifies IDH1 to regulate hepatoblastoma cell cycle and glucose metabolism. BMC Cancer 25, 1304 (2025). https://doi.org/10.1186/s12885-025-14644-5

Image Credits: Scienmag.com

DOI: https://doi.org/10.1186/s12885-025-14644-5