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Ultrasound and fine-needle aspiration initially suggested a benign thyroid lesion, leading to diagnostic and therapeutic right thyroid lobectomy. Histopathology with immunohistochemistry confirmed metastatic pulmonary adenocarcinoma involving the thyroid. Imaging showed no additional metastases, aside from an indeterminate small lung nodule. The report emphasizes integrating clinical history, imaging, and immunohistochemistry and highlights the need for long-term surveillance after prolonged disease-free intervals.",{"@graph":69,"@context":123},[70,84,106],{"@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/delayed-thyroid-metastasis-of-lung-adenocarcinoma-mimicking-primary-thyroid-carcinoma-a-case-report/354422/",{"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/delayed-thyroid-metastasis-of-lung-adenocarcinoma-mimicking-primary-thyroid-carcinoma-a-case-report/354422.png","ImageObject",300,407,{"name":92,"@type":93},"Blitz","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-29","2026-09-22",true,{"@type":102,"interactionType":103,"userInteractionCount":105},"InteractionCounter",{"@type":104},"ViewAction",11,{"@type":107,"mainEntity":108},"FAQPage",[109,115,119],{"name":110,"@type":111,"acceptedAnswer":112},"Why can lung adenocarcinoma metastasis to the thyroid be misdiagnosed as primary thyroid carcinoma?","Question",{"text":113,"@type":114},"It can mimic primary thyroid neoplasms on imaging and cytology, especially when there is no synchronous metastatic disease or when metastasis occurs after a long disease-free interval.","Answer",{"name":116,"@type":111,"acceptedAnswer":117},"What diagnostic step clarified the patient’s thyroid lesion?",{"text":118,"@type":114},"Right thyroid lobectomy followed by histopathology supported by immunohistochemical analysis confirmed metastatic adenocarcinoma from a pulmonary origin.",{"name":120,"@type":111,"acceptedAnswer":121},"What role does immunohistochemistry play in distinguishing metastatic lesions from primary thyroid cancer?",{"text":122,"@type":114},"Immunohistochemistry is critical because it differentiates metastatic adenocarcinoma from primary thyroid carcinoma when cytology suggests a benign nodule and clinical history raises suspicion.","https://schema.org",{"og:url":83,"og:type":125,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":127,"canonical":83},"index,follow",{"doc_id":129,"site_id":62},354422,1790441738,{"code":4,"msg":5,"data":132},{"doc_id":129,"user_id":133,"nickname":92,"user_avatar":134,"doc_module":4,"category_id":34,"category_name":35,"doc_title":65,"doc_description":67,"doc_content":135,"file_id":136,"file_url":137,"file_type":138,"file_size":139,"view_count":105,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":34,"language":140,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":141,"faqs":142,"seo_title":143,"seo_description":67,"update_tm":144,"read_time":145},24464137899374,"https://us-avatar.wpscdn.com/davatar_3d24733baf745e90a7e4bdd5f77d97b2","e-ISSN 1941-5923  \n© Am J Case Rep, 2026; 27: e952744 DOI: 10. 12659/AJCR.952744  \nReceived: 2026.01.09  \nAccepted: 2026.04.24  \nAvailable online: 2026.05.11  \nPublished: 2026.06.30  \nAuthors’ Contribution: Study Design A  \nData Collection B Statistical Analysis C Data Interpretation D Manuscript Preparation E Literature Search F Funds Collection G  \nAD 1 ADF 2-4 BCE 1 BCEF 2 BCE 3  \nBCE 3  \nBCE 2  \nCorresponding Author: Financial support: Conflict of interest:  \nDelayed Thyroid Metastasis of Lung Adenocarcinoma Mimicking Primary Thyroid Carcinoma: A Case Report  \nYen Thi Le  Hau Xuan Nguyen Thai Hong Le Anh Tuan Doan Van Duong Thai Pham  Tuan Minh Vu  \nHoang Van Nguyen   \nHau Xuan Nguyen, e-mail: [nguyenxuanhau@hmu.edu.vn](nguyenxuanhau@hmu.edu.vn)[ ](nguyenxuanhau@hmu.edu.vn)None declared  \nNone declared  \n1 Department of Quan Su Medical Oncology, Vietnam National Cancer Hospital, Hanoi, Vietnam  \n2 Department of Oncology, Hanoi Medical University, Hanoi, Vietnam  \n3 Department of Quan Su 2 Surgery, Vietnam National Cancer Hospital, Hanoi, Vietnam  \n4 Oncology Center, Hanoi Medical University Hospital, Hanoi, Vietnam  \nPatient: Female, 69-year-old  \nFinal Diagnosis: Delayed thyroid metastasis of lung adenocarcinoma  \nSymptoms: A progressively enlarging anterior neck mass  \nClinical Procedure: —  \nSpecialty: Oncology  \nObjective: Rare coexistence of disease or pathology  \nBackground: Thyroid metastasis from lung cancer is uncommon, accounting for approximately 8.3% of all thyroid metastases, which themselves occur in only about 1.4% to 3% of patients undergoing thyroid surgery; it poses significant diagnostic challenges due to its clinical and cytological resemblance to primary thyroid neoplasms.  \nCase Report: We report the case of a 69-year-old woman with a history of non–small cell lung carcinoma (NSCLC) that had remained stable for 9 years, who presented with a progressively enlarging anterior neck mass. Ultrasound and fine-needle aspiration (FNA) initially suggested a benign thyroid lesion. However, given the marked interval growth of the nodule and the patient’s oncologic history, a right thyroid lobectomy was performed for diagnostic and therapeutic purposes. Histopathology supported by immunohistochemical analysis was consistent with the diagnosis of metastatic adenocarcinoma of pulmonary origin involving the thyroid. Imaging studies did not demonstrate additional metastatic sites, although a small pulmonary nodule of uncertain importance was noted. She was subsequently referred for systemic therapy. We analyze the diagnostic challenges, histopathologic characteristics, limitations of FNA, and the critical role of immunohistochemistry in differentiating metastatic lesions from primary thyroid carcinoma.  \nConclusions: This case highlights the potential for misdiagnosis of metastatic thyroid lesions, particularly when cytological findings suggest a benign nodule, and underscores the importance of integrating clinical history, imaging, and immunohistochemistry to achieve an accurate diagnosis. Long-term surveillance remains essential in cancer survivors, as metastatic disease can occur after a prolonged disease-free interval.  \nKeywords: Immunohistochemistry • Thyroid Nodule • Carcinoma, Non-Small-Cell Lung  \nAbbreviations: FNA, fine-needle aspiration; NSCLC, non–small cell lung carcinoma; IHC, immunohistochemistry Full-text PDF: [https://www.amjcaserep.com/abstract/index/idArt/952744](https://www.amjcaserep.com/abstract/index/idArt/952744)  \n2313  —  3  25  \nPublisher’s note: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher  \nThis work is licensed under Creative Commons AttributionNonCommercial-NoDerivatives 4.0 International (","cbCaipopiFgInFhO","https://ap.wps.com/l/cbCaipopiFgInFhO","pdf",2495834,"English","# Introduction\n# Case Report\n# Conclusions","[{\"question\":\"Why can lung adenocarcinoma metastasis to the thyroid be misdiagnosed as primary thyroid carcinoma?\",\"answer\":\"It can mimic primary thyroid neoplasms on imaging and cytology, especially when there is no synchronous metastatic disease or when metastasis occurs after a long disease-free interval.\"},{\"question\":\"What diagnostic step clarified the patient’s thyroid lesion?\",\"answer\":\"Right thyroid lobectomy followed by histopathology supported by immunohistochemical analysis confirmed metastatic adenocarcinoma from a pulmonary origin.\"},{\"question\":\"What role does immunohistochemistry play in distinguishing metastatic lesions from primary thyroid cancer?\",\"answer\":\"Immunohistochemistry is critical because it differentiates metastatic adenocarcinoma from primary thyroid carcinoma when cytology suggests a benign nodule and clinical history raises suspicion.\"}]","Delayed Thyroid Metastasis of Lung Adenocarcinoma Mimicking Primary Thyroid Carcinoma - A Case Report | PDF",1790110566,18]