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.

Purpose To investigate the clinicopathological and molecular genetic characteristics of epithelioid inflammatory myofibroblastic sarcoma(EIMS)in children.Methods Clini-cal data of 7 cases of EIMS in children was collected,the ex-pression of ALK,CD30,desmin,SMA,CK,Ki67,etc.was detected with immunohistochemistry EnVision method,ALK gene disruption and rearrangement was detected using FISH method,and ALK gene fusion was examined by NGS sequen-cing.Clinical and pathological characteristics was analyzed and relevant literatures were reviewed.Results Children aged from 6 months to 12 years.There were 3 cases in abdomen,1 case in intestinal wall,1 case in vocal cord,1 case in pleura and 1 case in maxillary sinus.Multiple in 6 cases and single in 1 case.Im-aging showed soft tissue shadow.Pathological examination showed that tumor cells were various in shape,including small round,spindle-shaped or larger round.There were abundant cy-toplasm with small or inconspicuous nucleoli,ganglion cell-like cells was unconspicuous.There were different cell atypia,hy-perplasia,sparseness or both of background collagen.The main inflammatory cells were lymphocytes with scattered neutrophils,and few plasma cells.Immunohistochemistry,tumor cells ex-pressed ALK,CD30,desmin,SMA,and CK,Ki67 were ex-pressed in tumor cells(3％-40％).ALK split probes were positive in 4 cases,and RANBP2-ALK fusion was found in 3 ca-ses by next generation sequencing.All 7 cases were treated by surgery,5 cases underwent further postoperative treatment(3 cases received chemotherapy and targeted drug therapy,1 case received radiotherapy and chemotherapy,and 1 case received ra-diotherapy).During the follow-up of 1-60 months,2 cases died,1 case recurred and 4 cases survived without tumor.Con-clusion EIMS in children has a wide range of onset ages,and is common in abdominal omentum.The clinical manifestations and imaging are not special,most of them are multiple,and the tumor cells are diverse.Immunohistochemical and FISH detec-tion are helpful for diagnosis of EIMS.

Purpose To study the clinical and pathological features of angiomatoid fibrous histocytoma(AFH)and to ex-plore its diagnosis,differential diagnosis and prognosis.Meth-ods The clinicopathological and follow-up data were analyzed in 14 cases of AFH,and the literatures were reviewed.Results There were 11 males and 3 females.The age ranged from 11 months to 12 years and 11 months,with average 5.9 years.3 cases were located in limbs,and 5 cases in trunk,5 cases in head and neck region,and 1 of intracranial tumor.Histological-ly,14 cases were composed of fibrous capsules and lymphocyte sheaths,and cell nucleus were vacuolar,forming fascicles with focal whirling and synteny.Intralesional pseudoangiomatous spaces were noted in 9 cases.Calcification was found in 2 ca-ses.2 cases showed high mitotic acticity(11/10 HPF).Scle-rosing and/or myxoid stroma was seen in 3 cases.Tumors were immunopositive for desmin(10/14),EMA(12/14),CD99(12/14),SMA(9/12),ALK(7/8),and the average of Ki67 index was 16％.7 cases harbored EWSR1 rearrangenent(part-ner gene not identified),2 cases had EWSR1-ATF1 fusion and 2 EWSR1-CREB1 fusion.Clinical follow-up information was a-vailable for 14 cases(average 46 months).All the 14 cases were alive without recurrence and metastasis.Conclusion AFH is a borderline or low-grade malignant tumor,often demon-strates indolent behavior in children,but rarely recurs and me-tastasizes.The diagnosis and differential diagnosis require a comprehensive analysis of clinical features,histopathologic changes,immunohistochemical finding and EWSR1 or FUS gene detection results.

WHO firstly published the classification of paediatric tumours, in which genetic tumour syndromes were introduced as a separate chapter, covering the clinicopathological features, molecular genetic alterations, and diagnostic criteria of various tumor susceptibility syndromes common in children. This article briefly introduces and interprets 5 hotspot genetic tumour syndromes (neurofibromatosis type 1, naevoid basal cell carcinoma syndrome, von Hippel-Lindau syndrome, familial adenomatous polyposis and xeroderma pigmentosum) based on relevant literature, in order to bring new perspectives and insights to pathologists and clinicians.

Objective:To investigate the relationship between 1p/16q loss of heterozygosity (LOH) and 1p gain in Wilms tumor and their clinicopathologic characteristics and prognosis.Methods:A total of 175 Wilms tumor samples received from the Department of Pathology, Beijing Children′s Hospital from September 2019 to August 2022 were retrospectively analyzed. The histopathologic type and presence of lymph node involvement were evaluated by two pathologists. The clinical data including patients′gender, age, tumor location, preoperative chemotherapy, and tumor stage were summarized. Fluorescence in situ hybridization (FISH) was done to detect 1p/16q LOH and 1p gain and their correlation with the clinicopathological features and prognosis were analyzed.Results:Among the 175 samples, 86 cases (49.1%) were male and 89 (50.9%) were female. The mean age was (3.5±2.9) years, and the median age was 2.6 years. There were 26 (14.9%) cases with 1p LOH, 28 (16.0%) cases with 16q LOH, 10 (5.7%) cases of LOH at both 1p and 16q, and 53 (30.3%) cases with 1q gain. 1q gain was significantly associated with 1p LOH ( P<0.01) and 16q LOH ( P<0.01). There were significant differences ( P<0.01) between 1q gain, 1p LOH and 16q LOH among different age groups. The rate of 16q LOH in the high-risk histopathological subtype (50.0%) was significantly higher than that in the intermediate-risk subtype (13.6%, P<0.05). The frequency of 1q gain, 1p LOH, and 16q LOH in children with advanced clinical stages (Ⅲ and Ⅳ) was significantly higher than that in children with early clinical stages (Ⅰ and Ⅱ). 1q gain, 1p LOH, and 16q LOH showed no significant correlation with gender, unilateral or bilateral disease, chemotherapy, or lymph node metastasis. The progression-free survival (PFS) time for patients with 1q gain and 1p LOH was significantly shorter than those without these aberrations ( P<0.05). Additionally, the PFS time of patients with 16q LOH was slightly shorter than those with normal 16q, although the difference was not statistically significant. Patients with stage Ⅲ to Ⅳ disease exhibiting 1q gain or 1p LOH had a significantly higher relative risk of recurrence, metastasis, and mortality. Conclusions:1p/16q LOH and 1q gain are associated with age, high-risk histological type, and clinical stage in Wilms tumor. 1q gain and 1p LOH are significantly correlated with the prognosis of Wilms tumor.

Objective:To investigate the clinicopathological features, immunophenotype and molecular genetic characteristics of congenital spindle cell/sclerosing rhabdomyosarcoma.Methods:Sixteen cases (including 10 consultation cases) of congenital spindle cell/sclerosing rhabdomyosarcoma diagnosed at the Beijing Children′s Hospital, Capital Medical University, Beijing China, from April 2017 to January 2022 were collected. These cases were evaluated for clinical profiles, histomorphological features, immunophenotype and molecular characteristics.Results:Among the 16 patients, 9 were male and 7 were female. Five cases were present during maternal pregnancy and 11 cases were found immediately after birth. The tumors were located in the chest wall, low back, retroperitoneum, extremities or perineum. The tumors consisted of fasciculated spindle-shaped cells with localized mesenchymal sclerosis and vitreous metaplasia. Immunohistochemistry showed that the tumor cells expressed Desmin, Myogenin, MyoD1, SMA, CD56 and ALK to varying degrees, but not other markers such as CD34, CD99, pan-TRK, S-100 and BCOR. FISH analyses with NCOA2 (8q13) and VGLL2 (6q22) gene breakage probes revealed a breakage translocation in chromosome NCOA2 (8q13) in 4 cases (4/11). In the 6 cases subject to sequencing, a mutation at the p.L122R locus of MYOD1 gene was detected in 1 case (1/6). Two cases were examined by electron microscopy, which showed bundle-arranged myofilaments with some primitive myofilament formation. Five cases were resected with simple surgery, 2 cases were biopsied and followed up with observation only, and 9 cases were treated with surgery and adjuvant chemotherapy. Follow-up was available in 12 cases. At the end of the follow-up, 2 of the 12 patients developed local recurrences and 2 patients survived with disease.Conclusions:Congenital spindle cell/sclerosing rhabdomyosarcoma is a rare subtype of congenital rhabdomyosarcoma. It more commonly occurs in the chest, back and lower limbs of infants than other sites. NCOA2/VGLL2 gene fusion seems to be the most common genetic change. Its prognosis is better than other subtypes of rhabdomyosarcoma and those in adolescents and adults with the same subtype. Analysis and summary of its clinicopathological features can help differentiate it from other soft tissue tumors in infants and children and provide the information for appropriate treatments.

Objective:To analyze the clinical characteristics and prognosis of infants with rhabdomyosarcoma (RMS), thus enhancing the understanding of this disease.Methods:Clinical data of all RMS patients younger than 12 months treated in the Hematology Oncology Center, Beijing Children′s Hospital, Capital Medical University from May 2006 to June 2019 were retrospectively analyzed, including the age, gender, histological type, tumor primary site, tumor size, and the prognosis.Patients were followed up until December 31, 2019.The 3-year event free survival (EFS) rate of children was performed by plotting the Kaplan-Meier survival curves.Results:A total of 15 RMS children younger than 12 months were enrolled, accounting for 4.9% of all RMS cases in the same period, including 6 males and 9 females.The median age at diagnosis was 7.0 months (3.0-11.5 months). Classified by the primary site, 40.0% (6 cases) located in the head and neck, followed by 26.7% (4 cases) located in the limbs, 26.7% (4 cases) located in other parts, and 6.7% (1 case) located in the urogenital system.Embryonal RMS, alveolar RMS and spindle cell RMS accounted for 46.6% (7 cases), 26.7% (4 cases), and 26.7% (4 cases), respectively.Ten cases (66.7%) were stage Intergroup Rhabdomyosarcoma Study (IRS)-Ⅲ and 1 case (6.7%) was in stage Ⅳ.There were 10 cases (66.6%) in the middle-risk group, 4 cases (26.7%) in the low-risk group, and 1 case (6.7%) in the high-risk group.Two cases had a larger than 5 cm primary tumor; lymph node involvement was confirmed in 3 cases, and pulmonary metastasis occurred in 1 case at the time of diagnosis.All children were treated with chemotherapy, and 13 cases received postoperative chemotherapy and 1 case received preoperative chemotherapy.One case were not operated.Only 3 children underwent radiotherapy, including 1 case underwent particle implantation and 2 cases received external radiotherapy.Among the 15 children with RMS, 5 cases had relapse and disease progression with the 3-year EFS rate of (59.1±14.5)%, and 2 died with the 3-year overall survival rate of (80.8±12.6)%.Conclusions:The median age of diagnosis of RMS in single-center infants is 7 months.Head and neck are the most common primary sites of RMS.Nearly 50% of the children have the primary site of RMS with poor prognosis.More than a quarter of the pathological subtypes are the spindle cell type.Local treatment significantly influences the local progression or recurrence of RMS.

Objective:To study the clinicopathologic features, and the diagnosis and differential diagnosis of mycobacterial spindle cell pseudotumor in children.Methods:The clinical data, histopathological features, immunophenotype and special staining of 2 mycobacterial spindle cell pseudotumors were analyzed. The related literatures were reviewed.Results:The age of the two boys was 11 months and 22 months respectively, but their clinical symptoms became apparent at the age of about 4 months. The lesions involved lymph nodes and skin. The first patient also had fever for more than 4 months. Both patients received anti-inflammatory treatment in the outside hospital, but had no obvious improvements of the symptoms. A tumor resection was performed at the outside hospital. Histologically, mycobacterial spindle cell pseudotumor consisted of bland spindle cells, which formed fascicles, without any obvious atypia and mitoses. The cell nuclei were vesicular, with small nucleoli and abundant cytoplasm in some of the cases. The spindle cells expressed histiocyte-associated markers, such as CD68. The Ki-67 proliferation index was low. The mycobacteria were usually readily highlighted by acid-fast staining, which located in the cytoplasm of proliferative spindle cells. In the first case, there was obstructive jaundice because of the progressive enlargement of live portal lymph nodes and systemic disseminated lesions. The second patient had disease recurrence after only operation, and gradually developed other skin nodules and superficial lymph node enlargement. The high-throughput molecular analysis of the skin biopsy confirmed the diagnosis of mycobacterium tuberculosis. After 11 days of anti-tuberculosis treatment, the patient′s condition improved significantly.Conclusions:Mycobacterial spindle cell pseudotumor in children is a very rare benign lesion. It is characterized by spindle-histiocyte proliferation caused by mycobacterium infection. An acid-fast stain appears necessary for confirming the diagnosis.

Objective:To investigate the clinicopathologic characteristics, treatments, outcomes and mechanisms of hemolytic uremic syndrome (HUS) complicated with IgA nephropathy (IgAN).Methods:The clinical manifestations, treatments, prognosis and histopathological features of renal biopsy tissues were analyzed in two cases of HUS complicated with IgAN from Beijing Children′s Hospital, Capital Medical University using light microscopy, immunofluorescence detection and electron microscopy. The related literatures were also reviewed.Results:The clinical manifestations were microvascular hemolytic anemia, thrombocytopenia, acute renal impairment with hematuria, proteinuria, and positive anti-H factor antibody. Histological findings confirmed presence of both HUS and IgAN. Histological features included glomerular mesangial and stromal hyperplasia with endothelial cell proliferation, capillary stenosis, arteriolar thickening, and glomerular ischemia and capillary dilatation. Immunofluorescence detection showed diffuse IgA deposition in the glomerular mesangial matrix. Electron microscopy showed proliferation of mesangial and endothelial cells, thickening of the inner layer of the glomerular basement membrane, deposition of massive electronic densification in the mesangial region, and shrinkage of the segmental basement membrane. The two children were very responsive to plasma exchange and steroid treatments. However, their urine protein and occult blood tests remained continuously positive during the follow-up of 5 years 7 months and 8 months respectively.Conclusions:HUS complicated with IgAN is rare. The diagnosis relies on various pathological examinations, which require the combination of light microscopy, immunofluorescence detection and electron microscopy. Plasma exchange and steroid treatments are effective. However, the long-term prognosis is concerning and may relate to pathological grade and secondary factors. The mechanism of connecting HUS and IgAN is unknown, but may be caused by prodromal or secondary factors.

Objective: To investigate the clinicopathological manifestations, molecular genetic, diagnostic histology and differential diagnosis of alveolar soft part sarcoma (ASPS) in children. Methods: A total of 13 cases of ASPS diagnosed at Beijing Children′s Hospital from August 2009 to November 2018 were collected. HE staining, histochemical staining for PAS and D-PAS, immunohistochemical (IHC) staining for TFE3, INI1 and CD68 and florescence in situ hybridization (FISH) for TFE3 gene translocation were performed. Results: There were four males and nine females, age ranged from 1 year and 2 months to 13 years and 8 months (mean 7.8 years); and four patients were under 5 years old. Histologically, the tumors showed a distinctive and characteristic nested or organoid growth pattern (11 cases) or solid, diffuse growth (2 cases). The tumor cells possessed abundant eosinophilic, or glycogen-rich and clear to vacuolated cytoplasm. The chromatin was relatively dispersed, with prominent and pleomorphic nucleoli; mitotic figures were rare. Vascular invasion was frequently seen. IHC staining showed specific nuclear TFE3 staining. The tumor cells were also positive for INI1,CD68 and vimentin; but were negative for MyoD1, Myogenin, CK and S-100 protein. Seven cases showed PAS and D-PAS staining, with fuchsia acicular or rod-shaped crystals in tumor cytoplasm. Nine cases showed TFE3 break-apart signals by FISH. Conclusions ASPS is a rare soft tissue sarcoma in children. Compared with ASPA in adults, it has both similarities and unique clinicopathologic characteristics. The diagnosis needs to be confirmed by combining clinical, pathologic, IHC and genetic testing.