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Rhabdomyosarcoma of the extremities present with two main challenges: correct evaluation of initial regional nodal involvement and define adequate local treatment. Methods Pediatric patients with localized rhabdomyosarcoma of the extremity included in the EpSSG‐RMS2005 study between 2005 and 2014 were evaluated for staging, treatment, and survival. The outcome was compared to the preceding European SIOP‐MMT studies. Results Of the 162 patients included, histology was unfavorable in 113 (70%), 124 (77%) were younger than 10 years, 128 (79%) were IRS III, and 47 (29%) were node‐positive. A regional node biopsy was performed in 97 patients (60%) and modified the lymph node stage in 15/97 (16%). Primary and delayed surgery was performed in 155 (96%) and radiotherapy delivered in 118 (73%) patients. Relapse occurred in 61 cases (38%), local in 14 (23%), regional in 13 (21%), distant in 22 (36%), and combined relapse in 12 (20%) with five progressive diseases (8%) and four secondary tumors (7%). Five‐year event free (EFS) and overall survival (OS) were 58.4% (95%CI, 50.3‐65.7) and 71.7% (63.6‐78.4), respectively. In the previous studies MMT89 and MMT95, tumor surgery was performed in 32/53 (60%) and 74/82(90%), respectively, and radiotherapy delivered in 13/53 (25%) and 26/82 (30%), respectively. Five‐year EFS and OS were 35.6%, and 50.3% in MMT89 and 54.3% and 68.2% in the MMT95 study. Conclusions Even if the lymph node staging was not always complete according to the RMS2005 protocol, node sampling changed lymph node status in a significant number of patients. Despite the higher rate of patients treated with locoregional radiotherapy, survival in RMS2005 did not improve compared to the previous European SIOP‐MMT95 study., Adequate staging is important for the treatment of extremity RMS. Despite local therapy intensification, survival in RMS2005 did not improve compared to the previous European SIOP‐MMT95 study.

Rhabdomyosarcoma of the perianal/perineal region (PRMS) is rare, with poor survival and limited understanding of the functional consequences of treatment.International Society of Pediatric Oncology (SIOP) malignant mesenchymal tumor (MMT) 95, Italian RMS 96, and European paediatric Soft tissue sarcoma Study Group (EpSSG) RMS 2005 studies were interrogated to identify factors that impact survival; in RMS 2005, functional outcomes were analyzed.Fifty patients (nonmetastatic) were identified, median age 6.4 years (range: 0.1-19.6): 29 male, 21 female. Tumors were5 cm in 33 patients. Histopathological subtype was alveolar in 35. Lymph nodes were involved in 23 patients. In RMS 2005, 16/21 (76%) tested alveolar tumors had positive FOXO1 fusion status. Diagnostic biopsy was performed in 37. Primary resection (13) was complete (R0) in one. Delayed primary excision (16) was complete in three. Radiotherapy (RT) in 34/50 patients included external beam (28), brachytherapy (3), and both (3). Nodal RT was given in 16/23 N1 patients (70%). Median follow-up of alive patients (29) was 84.1 months (range: 3.6-221.1). Relapse or progression occurred in 24 patients (48%), 87% were fatal and most events (63%) were locoregional. Five-year event-free survival (EFS) was 47.8 (95% CI: 32.8-61.3), and 5-year overall survival (OS) was 52.6 (95% CI: 36.7-66.2), with age ≥10 years and tumor size5 cm impacting 5-year EFS and OS (p .05). Functional outcome data showed bowel, genito-urinary, and psychological issues; fecal incontinence in four of 21 survivors, and urinary symptoms in two of 21.About 60% of patients with nonmetastatic PRMS survive; older patients and those with large tumors have the worst outcomes. Biopsy should be the initial procedure, and definitive local therapy individualized. Quality-of-life and functional studies are needed to better understand the consequences of treatment.

Loss of histone 3 lysine 27 trimethylation (H3K27me3) has been described as a diagnostic marker for malignant peripheral nerve sheath tumor (MPNST), also discriminating MPNST with rhabdomyoblastic differentiation (malignant Triton tumor) from rhabdomyosarcoma (RMS). We studied the immunohistochemical expression of H3K27me3 in embryonal RMSs (ERMSs), performed methylation profiling in order to support the diagnosis and RNA-sequencing for comparison of the transcriptome of H3K27me3-positive and -negative cases. Of the 25 ERMS patients, 17 were males and 8 were females with an age range from 1 to 67 years (median, 6 years). None were known with neurofibromatosis type 1. One patient had Li-Fraumeni syndrome. Tumor localization included paratesticular (n = 9), genitourinary (n = 6), head/neck (n = 5), retroperitoneal (n = 4) and lower arm (n = 1). Five MPNSTs served as reference group. All ERMS had classical features including a variable spindle cell component. Immunohistochemical loss (partial or complete) of H3K27me3 was detected in 18/25 cases (72%). Based on methylation profiling, 22/22 cases were classified as ERMS. Using RNA sequencing, the ERMS group (n = 14) had a distinct gene expression profile in contrast to MPNSTs, confirming that the H3K27me3 negative ERMS cases do not represent malignant Triton tumors. When comparing H3K27me3-negative and -positive ERMSs, gene set enrichment analysis revealed differential expression of genes related to histone acetylation and normal muscle function with H3K27me3 negative ERMSs being associated with acetylation. Conclusion: Loss of H3K27me3 frequently occurs in ERMSs and correlates with H3K27 acetylation. H3K27me3 is not a suitable marker to differentiate ERMS (with spindle cell features) from malignant Triton tumor.