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The diagnosis of solid pseudopapillary neoplasm of the pancreas (SPN) can be challenging due to potential confusion with other pancreatic neoplasms, particularly pancreatic neuroendocrine tumors (NETs), using current pathological diagnostic markers. We conducted a comprehensive analysis of bulk RNA sequencing data from SPNs, NETs, and normal pancreas, followed by experimental validation. This analysis revealed an increased accumulation of peroxisomes in SPNs. Moreover, we observed significant upregulation of the peroxisome marker ABCD1 in both primary and metastatic SPN samples compared with normal pancreas and NETs. To further investigate the potential utility of ABCD1 as a diagnostic marker for SPN via immunohistochemistry staining, we conducted verification in a large-scale patient cohort with pancreatic tumors, including 127 SPN (111 primary, 16 metastatic samples), 108 NET (98 nonfunctional pancreatic neuroendocrine tumor, NF-NET, and 10 functional pancreatic neuroendocrine tumor, F-NET), 9 acinar cell carcinoma (ACC), 3 pancreatoblastoma (PB), 54 pancreatic ductal adenocarcinoma (PDAC), 20 pancreatic serous cystadenoma (SCA), 19 pancreatic mucinous cystadenoma (MCA), 12 pancreatic ductal intraepithelial neoplasia (PanIN) and 5 intraductal papillary mucinous neoplasm (IPMN) samples. Our results indicate that ABCD1 holds promise as an easily applicable diagnostic marker with exceptional efficacy (AUC=0.999, sensitivity=99.10%, specificity=100%) for differentiating SPN from NET and other pancreatic neoplasms through immunohistochemical staining., Competing Interests: Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc.)

Purpose: Recent studies claim that immune checkpoint inhibitors are effective in defective mismatch repair (dMMR) cancers. This raises the question of whether similar therapies are effective in PanNETs (pancreatic neuroendocrine tumors); however, in general, assessment of MMR status in PanNETs has been inconsistent in previous studies. MGMT (O6-methylguanine-DNA methyltransferase) is potentially important for guiding temozolomide (TMZ) therapy in glioblastoma. The number of reports on MGMT expression and promoter methylation in PanNETs are limited., Methods: In this study we assessed the expression of MGMT and MMR proteins MSH2, MSH6, MLH1 and PMS2 in a series of PanNETs by IHC. The methylation status of MGMT and MMR genes in a subset of PanNETs was further assessed by MS-MLPA analysis. Survival curves were constructed using the Kaplan-Meier method, and differences were assessed using the log-rank test. Multivariate Cox proportional hazards regression models were used to determine the prognostic value of the variables., Results: According to evaluation criteria for mismatch repair defects, none of PanNETs shown nuclear staining loss for MSH2, MSH6, MLH1, and PMS2. MGMT low-intensity PanNETs were more commonly found in higher grade, higher Ki67 index and non-functional tumors (P < 0.05). In multivariate analysis, stage III-IV and low-intensity MGMT were shown to be independent risk factors for progression of PanNETs in the entire cohort, non-functioning subgroup and G2 subgroup (P < 0.05 for all). MGMT promoter methylation tended to be higher in the group with low expression of MGMT, However, methylation of MGMT did not statistically correlate with low expression of MGMT (P = 0.153)., Conclusions: In conclusion, our study suggests that decreased expression of MGMT but not MMR is associated with a higher risk of progression of pancreatic neuroendocrine tumors., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background: Primary grade 2 neuroendocrine tumors of the cervix in female patients are rare and have a highly aggressive clinical course. This study is aimed to analyse the diagnosis, genetic changes, management and prognosis of these tumors and investigate whether the genetic alterations could provide more useful information to guide the molecular characterization and potential individualized treatment of grade 2 cervical neuroendocrine tumors., Methods: The clinical records of all three patients diagnosed as primary grade 2 neuroendocrine tumors of the cervix in Peking Union Medical College Hospital (PUMCH) from 2011 to 2018 were reviewed retrospectively. We investigated the morphology, immunophenotype and molecular abnormalities of all the cases. The follow-up data were also collected., Results: The age of the patients ranged from 46 to 69 years. All cases were in stage II and treated with surgery. The microscopic examination showed that the tumors took the form of nest-like, trabecular, sheet-like, "single file" strands or rosette-like structures. The mitotic figures ranged from 2 to 5 in every 10 high-power fields, and necrotic foci were observed in one case. Immunohistochemically, the tumor cells were positive for AE1/AE3, Cg A, Syn, CD56, P16, CAM5.2, and PGP9.5 and negative for ER, PR, P63, P40, CK7, and CK20. The expression of P53 showed as normal/wild-type pattern, and the proliferation index of Ki-67 ranged from 2 to 7%. A total of 560 genes were sequenced by next-generation sequencing for each patient, and nonsynonymous somatic mutations were identified in the three cases. Non-frameshift insertions of the MAGI1 and SLC45A were both observed in case 1, while we only observed the non-frameshift insertion of the MAGI1 in case 2 and the non-frameshift insertion of the SLC45A in case 3. Case 1 was treated with chemoradiotherapy before and after surgery. Cases 2 and 3 were treated with chemotherapy before and after surgery. The follow-up time ranged from 27 to 74 months. Cases 2 and 3 survived, while case 1 died., Conclusion: Cervical grade 2 neuroendocrine tumors are extremely rare. We presented the first mutation profile revealed by whole exome sequencing in a series of grade 2 cervical NETs along with their clinicopathological characteristics. Their genetic changes are different from those that take place in the gastrointestinal tract, pancreas and lung, which have gene changes in VEGF, RTKs or the mTOR signalling pathway. While changes in MAGI1 and SLC45L3 were observed in two of our cases and the case who had the gene changes of both MAGI1 and SLC45L3 died because of metastases to the liver and bone. The genetic alterations may provide more useful information to guide the molecular characterization and potential individualized treatment of grade 2 cervical neuroendocrine tumors.