Objective: To investigate the causal association between amino acids and the primary malignant bone tumor and its underlying mechanism. Methods: Genome-wide association study (GWAS) data of glycine, serine, arginine, glutamine, methionine, and leucine was sourced from the IEU OpenGWAS database and the GWAS Catalog. GWAS data of primary malignant bone tumor were obtained from the FinnGen database. Using each of the six amino acids as the exposure and primary malignant bone tumor as the outcome, two-sample Mendelian randomization (MR) analysis was performed with the inverse-variance weighted method as the primary approach. Multivariable MR analysis was employed to control for collinearity among amino acids. Sensitivity analyses were conducted using Cochran's Q test, MR-Egger regression and the MR Steiger test. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis and protein-protein interaction network analysis were explored to explore potential mechanisms and identify key genes. Results: MR analysis results indicated a statistically significant causal association between glycine and primary malignant bone tumor (OR=1.719, 95%CI: 1.083-2.728). No significant causal associations were found for the other five amino acids (all P>0.05). Multivariable MR analysis revealed that, after adjusting for the other five amino acids, confirmed a positive causal association between glycine and primary malignant bone tumor (OR=1.512, 95%CI: 1.125-2.031). Sensitivity analyses revealed no significant heterogeneity, horizontal pleiotropy, or reverse causality (all P>0.05). Genes associated with both glycine metabolism and primary malignant bone tumor were enriched in the JAK-STAT signaling pathway, with serine hydroxymethyltransferase 2 (SHMT2) identified as a key gene. Conclusion Higher glycine levels may increase the risk of primary malignant bone tumor via the SHMT2-JAK-STAT pathway.

Purpose To investigate the value of 18F-FDG PET/CT combined with MRI for detecting occult lymph node metastases in head and neck squamous cell carcinoma(HNSCC).Materials and Methods Eighteen patients with clinically node-negative,pathologically confirmed HNSCC were retrospectively enrolled from the Third Affiliated Hospital of Air Force Medical University from January 2022 to December 2023.All patients underwent preoperative 18F-FDG PET/CT and MRI,including 3D BRAVO high-resolution structural imaging,T2WI and diffusion-weighted imaging.Two nuclear medicine physicians qualitatively and semi-quantitatively assessed cervical lymph nodes for glucose metabolism and apparent diffusion coefficient(ADC)abnormalities.Using postoperative pathology as the gold standard,the diagnostic performance of PET,ADC and their combination for detecting occult metastases was compared.Results Among 54 dissected lymph nodes from 18 patients,12(22.2%)were pathologically confirmed as metastatic.Of 7 false-negative lymph nodes on diffusion weighted imaging,18F-FDG PET/CT correctly identified 4 as positive.18F-FDG PET/CT showed 6 false negatives and 6 false positives.The accuracies of 18F-FDG PET/CT and MRI for detecting occult metastases were 77.8%and 55.6%,respectively,while their combination achieved 91.1%accuracy(41/45).Metastatic lymph nodes exhibited higher maximum standardized uptake values(3.53±0.26 vs.2.71±0.14;t=3.17,P=0.008)and lower ADC values(0.91×10-3 mm2/s vs.1.07×10-3 mm2/s;t=4.15,P=0.001)compared with inflammatory nodes.Conclusion 18F-FDG PET/CT combined with diffusion weighted imaging improves detection of occult lymph node metastases in HNSCC and may guide surgical management.

Purpose To investigate the value of 18F-FDG PET/CT combined with MRI for detecting occult lymph node metastases in head and neck squamous cell carcinoma(HNSCC).Materials and Methods Eighteen patients with clinically node-negative,pathologically confirmed HNSCC were retrospectively enrolled from the Third Affiliated Hospital of Air Force Medical University from January 2022 to December 2023.All patients underwent preoperative 18F-FDG PET/CT and MRI,including 3D BRAVO high-resolution structural imaging,T2WI and diffusion-weighted imaging.Two nuclear medicine physicians qualitatively and semi-quantitatively assessed cervical lymph nodes for glucose metabolism and apparent diffusion coefficient(ADC)abnormalities.Using postoperative pathology as the gold standard,the diagnostic performance of PET,ADC and their combination for detecting occult metastases was compared.Results Among 54 dissected lymph nodes from 18 patients,12(22.2%)were pathologically confirmed as metastatic.Of 7 false-negative lymph nodes on diffusion weighted imaging,18F-FDG PET/CT correctly identified 4 as positive.18F-FDG PET/CT showed 6 false negatives and 6 false positives.The accuracies of 18F-FDG PET/CT and MRI for detecting occult metastases were 77.8%and 55.6%,respectively,while their combination achieved 91.1%accuracy(41/45).Metastatic lymph nodes exhibited higher maximum standardized uptake values(3.53±0.26 vs.2.71±0.14;t=3.17,P=0.008)and lower ADC values(0.91×10-3 mm2/s vs.1.07×10-3 mm2/s;t=4.15,P=0.001)compared with inflammatory nodes.Conclusion 18F-FDG PET/CT combined with diffusion weighted imaging improves detection of occult lymph node metastases in HNSCC and may guide surgical management.