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Primary renal neuroendocrine tumors (PRNETs) are exceptionally rare, with only about 160 reported cases worldwide. Because native neuroendocrine cells are not described in the renal parenchyma, cellular origin remains unresolved. A case of a 61-year-old woman with an incidentally detected left-sided PRNET illustrates non-specific clinical presentation, diagnostic complexity, and genomic heterogeneity, showing atypical molecular features lacking typical RCC or common NEN alterations.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":35,"@type":76,"position":81},"https://docshare.wps.com/document/healthcare/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/primary-renal-neuroendocrine-tumor-diagnostic-challenges-in-a-rare-entity-a-case-report/353774/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/primary-renal-neuroendocrine-tumor-diagnostic-challenges-in-a-rare-entity-a-case-report/353774.png","ImageObject",300,407,{"name":92,"@type":93},"Rowan","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-09-27","2026-09-22",true,{"@type":102,"interactionType":103,"userInteractionCount":81},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"Why are primary renal neuroendocrine tumors (PRNETs) difficult to diagnose?","Question",{"text":112,"@type":113},"PRNETs are extremely rare and present with non-specific symptoms that can mimic other renal diseases. Diagnosis relies on specialized histopathological evaluation with immunohistochemical markers and functional imaging.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"How was the reported PRNET case detected and what were the key clinical features?",{"text":117,"@type":113},"The tumor was incidentally discovered during routine examination in September 2024. At diagnosis, the patient reported no specific symptoms, and imaging showed a left renal mass without suspected metastatic lesions.",{"name":119,"@type":110,"acceptedAnswer":120},"What diagnostic methods are highlighted for PRNET in the case report?",{"text":121,"@type":113},"The report emphasizes histopathology with immunohistochemical markers such as chromogranin A and synaptophysin. It also highlights functional imaging using SSTR PET and discusses genomic characterization and literature review.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},353774,1790481273,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":34,"category_name":35,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":81,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":39,"language":139,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":140,"faqs":141,"seo_title":142,"seo_description":67,"update_tm":143,"read_time":46},1099514067415,"https://ap-avatar.wpscdn.com/avatar/100002539d78ffe74a7?x-image-process=image/resize,m_fixed,w_180,h_180&k=1779092875211072502","Case Report  \nPrimary Renal Neuroendocrine Tumor: Diagnostic Challenges ina Rare Entity—A Case Report  \nRaphaela D. Lewetag 1,2, Katharina Kluthe 3, Nils F. Trautwein 2,4, Ulrich M. Lauer 1,2,5,6, Christian la Fougère 2,4, Bence Sipos 1,2, Lars Zender 1,2,5,6, Clemens Hinterleitner 1,5,7, Stephan Singer 2,3,† and Martina Hinterleitner 1,2,5,*,†  \nReceived: 12 December 2025  \nRevised: 1 February 2026  \nAccepted: 4 February 2026  \nPublished: 6 February 2026  \nCopyright: © 2026 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license.  \n1 Department of Medical Oncology and Pneumology (Internal Medicine VIII), University Hospital Tuebingen, 72076 Tuebingen, Germany  \n2 ENETS Center of Excellence, University Hospital Tuebingen, 72076 Tuebingen, Germany; [christian.lafougere@med.uni-tuebingen.de](christian.lafougere@med.uni-tuebingen.de) (C.l.F.)  \n3 Department of Pathology, University Hospital Tuebingen, 72076 Tuebingen, Germany  \n4 Department of Nuclear Medicine and Clinical Molecular Imaging, University Hospital Tuebingen,  \n72076 Tuebingen, Germany  \n5 DFG Cluster of Excellence 2180 ‘Image-Guided and Functional Instructed Tumor Therapy’, University of Tuebingen, 72076 Tuebingen, Germany  \n6 German Cancer Consortium, German Cancer Research Center, 72070 Tuebingen, Germany  \n7 Cancer Biology and Genetics, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA  \n* Correspondence: martina.hinterleitner@med.uni-tuebingen.de † These authors contributed equally to this work.  \nSimple Summary  \nNeuroendocrine neoplasms (NENs) are rare and heterogeneous tumors. Primary renal neuroendocrine tumors (PRNETs) are exceptionally uncommon, with approximately 160 cases reported worldwide. Since PRNETs present with non-specific clinical symptoms and closely mimic more common renal neoplasms, diagnosis is challenging and relies on specialized pathological evaluation. Here, we report the case of a 61-year-old woman with an incidentally discovered left-sided PRNET, illustrating the diagnostic challenges and underscoring the genomic heterogeneity of these tumors.  \nAbstract  \nNeuroendocrine neoplasms (NENs) represent a rare, heterogeneous group of malignancies. Within this tumor entity, primary renal neuroendocrine tumors (PRNETs) are exceedingly rare, with only 160 cases reported worldwide. Due to the absence of native neuroendocrine cells in the renal parenchyma, their cellular origin remains unclear. Clinical and diagnostic challenges are reflected by the low incidence, non-specific clinical presentation, resemblance to common renal neoplasms, and the need for specialized histopathological diagnostic examination. Here, we present the case of a 61-year-old female with an incidentally diagnosed left-sided PRNET in September 2024 . This case highlights the diagnostic complexity of PRNET and, importantly, underscores its genomic heterogeneity. It demonstrates a lack of typical renal cell carcinoma (RCC) or common NEN-associated gene alterations, emphasizing their unique molecular landscape.  \nKeywords: neuroendocrine neoplasms; primary renal neuroendocrine tumor; immunohistochemistry; tumor genome sequencing; SSTR PET  \n1. Introduction  \nNeuroendocrine neoplasms (NENs) are a rare and heterogeneous group of solid tumors, accounting for 0.5–2.0% of all newly diagnosed malignancies [1] . They are classified into two groups with distinct biological characteristics: well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs) [2] . These neoplasms can originate from various anatomical sites, most commonly occurring in the gastrointestinal tract, including the pancreas (>60%), and the lungs (>20%) [3] . In contrast to these more prevalent locations, primary renal neuroendocrine tumors (PRNET) are extremely rare [4] . To date, there are approximately 160 cases reported worldwid","cbCaikI7AGip1pYq","https://ap.wps.com/l/cbCaikI7AGip1pYq","pdf",967565,"English","# Introduction\n# Case Report","[{\"question\":\"Why are primary renal neuroendocrine tumors (PRNETs) difficult to diagnose?\",\"answer\":\"PRNETs are extremely rare and present with non-specific symptoms that can mimic other renal diseases. Diagnosis relies on specialized histopathological evaluation with immunohistochemical markers and functional imaging.\"},{\"question\":\"How was the reported PRNET case detected and what were the key clinical features?\",\"answer\":\"The tumor was incidentally discovered during routine examination in September 2024. At diagnosis, the patient reported no specific symptoms, and imaging showed a left renal mass without suspected metastatic lesions.\"},{\"question\":\"What diagnostic methods are highlighted for PRNET in the case report?\",\"answer\":\"The report emphasizes histopathology with immunohistochemical markers such as chromogranin A and synaptophysin. It also highlights functional imaging using SSTR PET and discusses genomic characterization and literature review.\"}]","Primary Renal Neuroendocrine Tumor: Diagnostic Challenges in a Rare Entity - A Case Report | PDF",1790107160]