Pediatric tumors differ significantly from adult cancers, possessing unique developmental origins, histological features, and molecular genetic changes. With the rapid advancement of multi-omics technologies, such as genomics, transcriptomics, proteomics, and epigenetic analyses, the molecular characteristics of pediatric tumors have been extensively revealed, providing new possibilities for precision medicine. Concurrently, the integration of artificial intelligence and digital pathology has effectively enhanced diagnostic accuracy, presenting a broad scope for future development. While this progress positively impacts the pathological diagnosis of pediatric tumors, it also presents challenges related to data complexity, technology integration, and the promotion of clinical applications. This article aims to discuss the influence of molecular and artificial intelligence, as well as multimodal integrated pathological models on diagnosis and prognostic prediction of pediatric tumor, with the goal of fostering further exploration and in-depth research.

Objective:To investigate the clinicopathological and molecular genetic characteristics of pediatric tumors with DICER1 mutations.Methods:A total of 90 patients diagnosed with various types of pediatric tumors at Beijing Children′s Hospital, Capital Medical University, Beijing, China from July 2023 to September 2025 were included in this study. PCR amplification and Sanger sequencing were performed to detect the coding-region mutations of the DICER1 gene. The clinical, histopathological, and molecular genetic features of the cases with DICER1 mutation were then analyzed.Results:Among the 90 patients, 39 were male and 51 were female, with an age of onset ranging from 1 month to 17 years [median 7.13 (2.77, 10.37) years]. DICER1 mutations were detected in 37 patients (37/90, 41.1%). Among them, 9 cases harbored one mutation [6 pleuropulmonary blastomas (PPBs), 2 sex cord stromal tumors (SCSTs), and 1 cystic nephroma (CN)], 27 cases carried two mutations [10 PPBs, 3 anaplastic sarcomas of the kidney (ASKs), 3 SCSTs, 3 thyroid adenoma, 2 nodular thyroid goiters, 2 thyroid follicular lesions, 2 CN, 1 embryonal rhabdomyosarcoma, and 1 case with multiple primary tumors], and 1 case exhibited three mutations (bilateral ASKs). Despite variations in the site of origin, DICER1-mutant tumors shared several morphological features. Grossly, they presented as multilocular cystic, cystic-solid to solid masses. Microscopically, they exhibited a subepithelial layer of mesenchymal cells, with focal rhabdomyoblastic/chondroid/chondrosarcomatous differentiation, as well as cellular anaplasia. Germline testing using peripheral blood in the 31 patients with DICER1 mutation confirmed germline origin in 61.3% (19/31) of them. Parental analysis ( n=12) demonstrated genetic inheritance in 8 cases, predominantly from families with tumor history. Germline variants scattered throughout DICER1 and consisted of loss-of-function mutations (nonsense, frameshift, and splice-site). Somatic mutations showed distinct clustering in exons 24 and 25 hotspots (codons 1705, 1709, 1809, 1810 and 1813), primarily missense variants. Notably, one multiple primary tumor case harbored a somatic mosaic p.E1705K mutation. Conclusions:DICER1 mutations are frequently detected in pediatric PPB, CN, SCST, ASK, nodular thyroid goiter, thyroid adenoma, and genitourinary rhabdomyosarcoma, which often represent as the index case of DICER1 syndrome. Performing DICER1 mutation testing in these patients not only facilitates tumor diagnosis and secondary cancer surveillance, but also enables the comprehensive genetic risk assessment and management for patient′s family members.

In the past decade, governments, including the national, provincial, municipal, and others, have increased their investment in children′s health. Pathologists, especially pediatric pathologists, have greatly promoted the development and progress of pediatric pathology in China with the guidance of molecular pathological technology. This article reviews the cultivation of pediatric pathology talents, the application of new technologies, clinical pathological diagnosis and research, as well as many other aspects over the past decade, and looks forward to the future development of pediatric pathology.

Objective:To investigate a new method for rapid detection of the MYOD1 L122R mutation and to analyze the clinical and pathological characteristics of mutation-positive rhabdomyosarcoma.Methods:A MYOD1 mutation detection kit was developed using allele-specific Taqman fluorescence probe technology. A total of 80 rhabdomyosarcoma samples diagnosed at Beijing Children′s Hospital, Capital Medical University from June 2022 to June 2023 were collected for testing. The detection sensitivity, specificity, and consistency rate of the kit were compared with those of the gold standard Sanger sequencing. The demographic, histopathological, and molecular genetic characteristics of patients with MYOD1 mutations were analyzed.Results:Among the 80 rhabdomyosarcoma cases, there were 46 males and 34 females, with an age of onset ranging from 0 to 16 years [mean (6.0±4.4) years], including 32 embryonal rhabdomyosarcoma, 18 alveolar rhabdomyosarcoma, and 30 spindle cell/sclerosing rhabdomyosarcoma. The new kit screened a total of 11 mutations, of which 10 were spindle cell/sclerosing rhabdomyosarcoma and one was embryonal rhabdomyosarcoma. Patients with MYOD1 mutations were typically older (four cases over 10 years old) but could also occur in young children (the youngest being 3-year and 2-month-old). The primary sites were the head and neck region in eight cases, limbs in two cases, and pelvic cavity in one case. Among the six patients with available staging information at initial diagnosis, one was classified as stage 2 and five were stage 3, all of which were intermediate risk. Among the 11 mutation patients, six had recurrence and metastasis, with three deaths; the remaining patients had not shown tumor progression until last follow-up. Compared with the wild type group, the expression level of MYOD1 in mutation patients increased significantly ( χ2=10.66, P=0.01), while the event-free survival rate ( χ2=9.925, P<0.01) and overall survival ( χ2=4.53, P=0.03) rate decreased. Compared with Sanger sequencing, the kit achieved 100% sensitivity and specificity. The kit had a minimum mutation content detection limit of 2% and the reaction could be finished within 2 hours. Additionally, this kit might also be used to detect the expression of MYOD1, thereby aiding the diagnosis of rhabdomyosarcoma. Conclusions:The study has established a new method for accurate and rapid detection of MYOD1 mutation in rhabdomyosarcoma, particularly suitable for the formalin-fixed and paraffin-embedded samples in clinical settings. MYOD1 mutations more likely occur in spindle cell/sclerosing rhabdomyosarcoma of the head and neck region in children. Patients with MYOD1 mutations have an extremely poor prognosis, which is independent of clinical staging and grading. MYOD1 mutation detection in rhabdomyosarcoma has significant value for auxiliary diagnosis and prognostic assessment.

Objective:To analyze the clinical characteristics of children with head and neck rhabdomyosarcoma (RMS) and to summarize the mid-long term efficacy of Beijing Children′s Hospital Rhabdomyosarcoma 2006 (BCH-RMS-2006) regimen and China Children′s Cancer Group Rhabdomyosarcoma 2016 (CCCG-RMS-2016) regimen.Methods:A retrospective cohort study. Clinical data of 137 children with newly diagnosed head and neck RMS at Beijing Children′s Hospital, Capital Medical University from March 2013 to December 2021 were collected. Clinical characteristic of patients at disease onset and the therapeutic effects of patients treated with the BCH-RMS-2006 and CCCG-RMS-2016 regimens were compared. The treatments and outcomes of patients with recurrence were also summarized. Survival analysis was performed by Kaplan-Meier method, and Log-Rank test was used for comparison of survival rates between groups.Results:Among 137 patients, there were 80 males (58.4%) and 57 females (41.6%), the age of disease onset was 59 (34, 97) months. The primary site in the orbital, non-orbital non-parameningeal, and parameningeal area were 10 (7.3%), 47 (34.3%), and 80 (58.4%), respectively. Of all patients, 32 cases (23.4%) were treated with the BCH-RMS-2006 regimen and 105 (76.6%) cases were treated with the CCCG-RMS-2016 regimen. The follow-up time for the whole patients was 46 (20, 72) months, and the 5-year progression free survival (PFS) and overall survival (OS) rates for the whole children were (60.4±4.4)% and (69.3±4.0)%, respectively. The 5-year OS rate was higher in the CCCG-RMS-2016 group than in BCH-RMS-2006 group ((73.0±4.5)% vs. (56.6±4.4)%, χ2=4.57, P=0.029). For the parameningeal group, the 5-year OS rate was higher in the CCCG-RMS-2016 group (61 cases) than in BCH-RMS-2006 group (19 cases) ((57.3±7.6)% vs. (32.7±11.8)%, χ2=4.64, P=0.031). For the group with meningeal invasion risk factors, the 5-year OS rate was higher in the CCCG-RMS-2016 group (54 cases) than in BCH-RMS-2006 group (15 cases) ((57.7±7.7)% vs. (30.0±12.3)%, χ2=4.76, P=0.029). Among the 10 cases of orbital RMS, there was no recurrence. In the non-orbital non-parameningeal RMS group (47 cases), there were 13 (27.6%) recurrences, after re-treatment, 7 cases survived. In the parameningeal RMS group (80 cases), there were 40 (50.0%) recurrences, with only 7 cases surviving after re-treatment. Conclusions:The overall prognosis for patients with orbital and non-orbital non-parameningeal RMS is good. However, children with parameningeal RMS have a high recurrence rate, and the effectiveness of re-treatment after recurrence is poor. Compared with the BCH-RMS-2006 regimen, the CCCG-RMS-2016 regimen can improve the treatment efficacy of RMS in the meningeal region.

The latest published WHO Classification of Pediatric Tumors is the first to be independent of the WHO Classification of Tumors in adults, serving as an independent volume that covers the latest advances in clinical characteristics, histopathology, molecular pathology, pathogenesis, and treatment of multiple systems, multiple types of pediatric tumors. Among them, soft tissue tumors have been updated based on the Edition Ⅴ of WHO Classification of Tumors of Soft Tissue and Bone, and some molecularly defined pediatric soft tissue tumors have been emphasized. This article, based on literature, mainly interprets the specific types of tumors that occur exclusively in children in the WHO Classification of Pediatric Tumors of Soft Tissue.

The latest published WHO Classification of Pediatric Tumors is the first to be independent of the WHO Classification of Tumors in adults, serving as an independent volume that covers the latest advances in clinical characteristics, histopathology, molecular pathology, pathogenesis, and treatment of multiple systems, multiple types of pediatric tumors. Among them, soft tissue tumors have been updated based on the Edition Ⅴ of WHO Classification of Tumors of Soft Tissue and Bone, and some molecularly defined pediatric soft tissue tumors have been emphasized. This article, based on literature, mainly interprets the specific types of tumors that occur exclusively in children in the WHO Classification of Pediatric Tumors of Soft Tissue.

In the past decade, governments, including the national, provincial, municipal, and others, have increased their investment in children′s health. Pathologists, especially pediatric pathologists, have greatly promoted the development and progress of pediatric pathology in China with the guidance of molecular pathological technology. This article reviews the cultivation of pediatric pathology talents, the application of new technologies, clinical pathological diagnosis and research, as well as many other aspects over the past decade, and looks forward to the future development of pediatric pathology.

Objective:To investigate a new method for rapid detection of the MYOD1 L122R mutation and to analyze the clinical and pathological characteristics of mutation-positive rhabdomyosarcoma.Methods:A MYOD1 mutation detection kit was developed using allele-specific Taqman fluorescence probe technology. A total of 80 rhabdomyosarcoma samples diagnosed at Beijing Children′s Hospital, Capital Medical University from June 2022 to June 2023 were collected for testing. The detection sensitivity, specificity, and consistency rate of the kit were compared with those of the gold standard Sanger sequencing. The demographic, histopathological, and molecular genetic characteristics of patients with MYOD1 mutations were analyzed.Results:Among the 80 rhabdomyosarcoma cases, there were 46 males and 34 females, with an age of onset ranging from 0 to 16 years [mean (6.0±4.4) years], including 32 embryonal rhabdomyosarcoma, 18 alveolar rhabdomyosarcoma, and 30 spindle cell/sclerosing rhabdomyosarcoma. The new kit screened a total of 11 mutations, of which 10 were spindle cell/sclerosing rhabdomyosarcoma and one was embryonal rhabdomyosarcoma. Patients with MYOD1 mutations were typically older (four cases over 10 years old) but could also occur in young children (the youngest being 3-year and 2-month-old). The primary sites were the head and neck region in eight cases, limbs in two cases, and pelvic cavity in one case. Among the six patients with available staging information at initial diagnosis, one was classified as stage 2 and five were stage 3, all of which were intermediate risk. Among the 11 mutation patients, six had recurrence and metastasis, with three deaths; the remaining patients had not shown tumor progression until last follow-up. Compared with the wild type group, the expression level of MYOD1 in mutation patients increased significantly ( χ2=10.66, P=0.01), while the event-free survival rate ( χ2=9.925, P<0.01) and overall survival ( χ2=4.53, P=0.03) rate decreased. Compared with Sanger sequencing, the kit achieved 100% sensitivity and specificity. The kit had a minimum mutation content detection limit of 2% and the reaction could be finished within 2 hours. Additionally, this kit might also be used to detect the expression of MYOD1, thereby aiding the diagnosis of rhabdomyosarcoma. Conclusions:The study has established a new method for accurate and rapid detection of MYOD1 mutation in rhabdomyosarcoma, particularly suitable for the formalin-fixed and paraffin-embedded samples in clinical settings. MYOD1 mutations more likely occur in spindle cell/sclerosing rhabdomyosarcoma of the head and neck region in children. Patients with MYOD1 mutations have an extremely poor prognosis, which is independent of clinical staging and grading. MYOD1 mutation detection in rhabdomyosarcoma has significant value for auxiliary diagnosis and prognostic assessment.

Pediatric tumors differ significantly from adult cancers, possessing unique developmental origins, histological features, and molecular genetic changes. With the rapid advancement of multi-omics technologies, such as genomics, transcriptomics, proteomics, and epigenetic analyses, the molecular characteristics of pediatric tumors have been extensively revealed, providing new possibilities for precision medicine. Concurrently, the integration of artificial intelligence and digital pathology has effectively enhanced diagnostic accuracy, presenting a broad scope for future development. While this progress positively impacts the pathological diagnosis of pediatric tumors, it also presents challenges related to data complexity, technology integration, and the promotion of clinical applications. This article aims to discuss the influence of molecular and artificial intelligence, as well as multimodal integrated pathological models on diagnosis and prognostic prediction of pediatric tumor, with the goal of fostering further exploration and in-depth research.