Hyoung Soo Choi

Hepatoblastoma (HB) is the most common primary liver malignancy in children, predominantly affecting those younger than 3 years of age. Although the overall survival rate has improved significantly over the past few decades, standardized clinical practice guidelines for HB in Korea have been lacking. This clinical practice guideline was developed to provide evidence-based recommendations for the diagnosis and treatment of HB in children. A multidisciplinary working group comprising pediatric hematologists/oncologists, radiologists, surgeons, pathologists, and methodologists systematically reviewed the literature published up to May 2023. For pretreatment imaging, both abdominal computed tomography and magnetic resonance imaging are useful for PRE-Treatment EXTent of disease (PRETEXT) staging, with each modality offering distinct advantages. PRETEXT staging at diagnosis is recommended as it provides valuable prognostic information. For standard-risk HB (PRETEXT I–III without metastasis and alpha-fetoprotein ≥100 ng/mL), cisplatinbased chemotherapy without doxorubicin is recommended over cisplatin-doxorubicin combination therapy, as it demonstrates equivalent survival outcomes with fewer adverse effects. In carefully selected patients who are eligible for complete resection at diagnosis, upfront surgery without neoadjuvant chemotherapy should be considered to spare unnecessary chemotherapy and its toxicities. For patients with residual pulmonary metastases after chemotherapy, pulmonary metastasectomy should be considered. Sodium thiosulfate administration following cisplatin should be considered to reduce ototoxicity, although the supporting evidence is derived predominantly from standard-risk patients and its availability in Korea remains limited. Regarding histological subtypes, well-differentiated fetal HB is associated with favorable outcomes and may be treated with surgery alone, whereas the small cell undifferentiated pattern is no longer classified as a HB subtype and requires immunohistochemical and molecular testing to distinguish it from malignant rhabdoid tumor and other small round cell tumors. This guideline represents the first evidence-based clinical practice guideline for pediatric HB in Korea. It aims to standardize the diagnostic and therapeutic approaches, ultimately improving outcomes for Korean children with HB. Given the rarity of this tumor, international collaboration and prospective data collection remain essential for future guideline updates.

Soo Kyung Lee, Yun Young Choi, Anna Cho, Yong Sung Kim, Yeon Jung Lim and Hyoung Soo Choi. CPHO 2026;33:92-7. https://doi.org/10.15264/cpho.2026.33.2.92

Purpose Chronic myeloid leukemia (CML) in children, adolescents, and young adults is rare and differs from older adults. This study evaluated the outcomes of allogeneic hematopoietic stem cell transplantation (HSCT) in young Korean CML patients during the tyrosine kinase inhibitor (TKI) era.Materials and Methods A retrospective analysis of 35 CML patients aged < 40 years who underwent allogeneic HSCT from 2009 to 2019 was conducted using Korean Blood and Marrow Transplantation Registry data. Patients were grouped by age < 20 years at HSCT (group 1, n=15) and 20-40 years at HSCT (group 2, n=20). Survival outcomes including overall survival (OS), relapse-free survival (RFS), and event-free survival (EFS) were analyzed using the Kaplan-Meier method.Results The median time between diagnosis and HSCT was 8.9 months. All the patients achieved engraftment but platelet recovery was significantly slower in group 1 (p=0.034). Acute and chronic graft-versus-host disease occurred in 54.3% and 34.3%, respectively. Five-year OS, RFS, and EFS rates of total patients were 66.8%, 50.8%, and 47.6%, with better OS was observed in group 1 by multivariable analysis (p=0.048). Disease status at HSCT was a significant predictor of OS (p=0.028), RFS (p=0.003), and EFS (p=0.004). Disease progression occurred in 13 out of 35 patients (37.1%); treatment-related mortality accounted for 63.6% of deaths (7 out of 11).Conclusion When performed at a younger age, allogeneic HSCT result in superior outcome in CML. Achieving remission before HSCT is critical for improved outcomes, highlighting the importance of pretransplant remission via optimal TKI strategies and minimal residual disease monitoring.

Lee E, et al. Brain Tumor Res Treat. 2025 Apr;13(2):45-52. https://doi.org/10.14791/btrt.2024.0045

Choi HS, et al. Brain Tumor Res Treat. 2025 Apr;13(2):58-64. https://doi.org/10.14791/btrt.2025.0003

Bomi Lim, Anna Cho, Jaehyun Kim, Sang Mee Hwang, Soo Yeon Kim, Jong-Hee Chae and Hyoung Soo Choi. CPHO 2024;31:52-5. https://doi.org/10.15264/cpho.2024.31.2.52

Chueh HW, et al. J Korean Med Sci. 2024 May;39(18):e162. https://doi.org/10.3346/jkms.2024.39.e162

Park SW, et al. Pediatr Infect Vaccine. 2024 Apr;31(1):46-54. https://doi.org/10.14776/piv.2024.31.e15

The MYCC and MYCN loci are each associated with two upstream open reading frames (uORFs) potentially encoding small proteins (9–21 kDa). We previously demonstrated that uORFs mrtl and MYCHEX1 of MYCC are translated, and their protein products may function to regulate the expression of the “parent” oncogene. We hypothesized that a similar relationship might exist between MYCN and its two uORFs: MYCNOT and MNOP, and investigated the uORF‐encoded proteins associated with MYCN to confirm their expression and intracellular location in neuroblastoma and medulloblastoma cells and tissues. MNOP, MYCNOT, mrtl, and MYCHEX1 were readily detected via reverse transcription polymerase chain reaction and Western blot analysis in tumor cell lines. In tumor tissue, MNOP protein expression was confirmed; however, MCYNOT generated from alternative splicing MYCNΔ1b mRNA was not detected. Immunofluorescence staining of MYCNOT displayed multiple bright foci in the nucleus and diffuse staining in the cytoplasm, suggesting that this small protein may function in both the nucleus and cytoplasm. Upon JQ1 treatment, MYCN, MYCNOT, and mrtl decreased substantially or disappeared completely in three different tumor cell lines. Significant levels of apoptosis were observed in each pediatric embryonal tumor cell line but not T47D breast carcinoma cells, suggesting that response to JQ1 transcriptional inhibition is greatest in tumor cells, which depend on MYC to maintain an undifferentiated phenotype. In conclusion, both MYCN uORF‐encoded proteins MNOP and MYCNOT, together with the two MYCC uORF‐encoded proteins mrtl and MYCHEX1 were detected simultaneously in tumor cell lines and tumor tissues. These four distinct proteins are translated from the “5′‐untranslated region” of MYCN or MYCC mRNA and display consistent distribution patterns within the cell. Additional studies to further elucidate the physiological and pathological roles of these uORF‐encoded proteins are warranted, as insights gained could inform new strategies for modulating MYC‐family oncogenes by targeting their uORFs.

PurposeRenal tumors account for approximately 7% of all childhood cancers. These include Wilms tumor (WT), clear cell sarcoma of the kidney (CCSK), malignant rhabdoid tumor of the kidney (MRTK), renal cell carcinoma (RCC), congenital mesoblastic nephroma (CMN) and other rare tumors. We investigated the epidemiology of pediatric renal tumors in Korea.Materials and MethodsFrom January 2001 to December 2015, data of pediatric patients (0–18 years) newly-diagnosed with renal tumors at 26 hospitals were retrospectively analyzed.ResultsAmong 439 patients (male, 240), the most common tumor was WT (n=342, 77.9%), followed by RCC (n=36, 8.2%), CCSK (n=24, 5.5%), MRTK (n=16, 3.6%), CMN (n=12, 2.7%), and others (n=9, 2.1%). Median age at diagnosis was 27.1 months (range 0-225.5) and median follow-up duration was 88.5 months (range 0-211.6). Overall, 32 patients died, of whom 17, 11, 1, and 3 died of relapse, progressive disease, second malignant neoplasm, and treatment-related mortality. Five-year overall survival and event free survival were 97.2% and 84.8% in WT, 90.6% and 82.1% in RCC, 81.1% and 63.6% in CCSK, 60.3% and 56.2% in MRTK, and 100% and 91.7% in CMN, respectively (p < 0.001).ConclusionThe pediatric renal tumor types in Korea are similar to those previously reported in other countries. WT accounted for a large proportion and survival was excellent. Non-Wilms renal tumors included a variety of tumors and showed inferior outcome, especially MRTK. Further efforts are necessary to optimize the treatment and analyze the genetic characteristics of pediatric renal tumors in Korea.