{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,1]],"date-time":"2026-06-01T14:10:37Z","timestamp":1780323037979,"version":"3.54.1"},"reference-count":9,"publisher":"BMJ","issue":"6","content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Case Rep"],"accepted":{"date-parts":[[2026,5,12]]},"published-print":{"date-parts":[[2026,6]]},"abstract":"<jats:p>A man in his early 70s with a prior history of high-grade urothelial carcinoma presented with a large left upper lobe lung mass detected on imaging. Endobronchial biopsy demonstrated non-small cell carcinoma with squamoid morphology and diffuse p40 positivity, supporting an initial diagnosis of primary pulmonary squamous cell carcinoma. The patient received neoadjuvant platinum-based chemotherapy and immunotherapy without a significant radiographic response. Subsequent lobectomy revealed a carcinoma with prominent papillary architecture and an immunophenotype characterised by cytokeratin 7, cytokeratin 20, GATA binding protein 3 (GATA3) and p40 positivity, supporting metastatic urothelial carcinoma. Review of the original biopsy confirmed limited tissue with overlapping squamoid features. This case highlights a potential diagnostic pitfall: metastatic urothelial carcinoma may demonstrate diffuse p40 expression and mimic primary pulmonary squamous cell carcinoma on limited lung biopsy, emphasising the importance of expanded immunohistochemical panels and clinicopathologic correlation.<\/jats:p>","DOI":"10.1136\/bcr-2026-272914","type":"journal-article","created":{"date-parts":[[2026,6,1]],"date-time":"2026-06-01T13:10:10Z","timestamp":1780319410000},"page":"e272914","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["p40-positive metastatic urothelial carcinoma mimicking primary pulmonary squamous cell carcinoma on limited lung biopsy"],"prefix":"10.1136","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4387-9727","authenticated-orcid":false,"given":"Yanina","family":"Nikolaus","sequence":"first","affiliation":[{"name":"Pathology, Marshall University Joan C Edwards School of Medicine, Huntington, West Virginia, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2026,6,1]]},"reference":[{"key":"2026060106100756000_19.6.e272914.1","doi-asserted-by":"publisher","DOI":"10.1038\/modpathol.2014.158"},{"key":"2026060106100756000_19.6.e272914.2","doi-asserted-by":"publisher","DOI":"10.1016\/j.eururo.2016.02.029"},{"key":"2026060106100756000_19.6.e272914.3","doi-asserted-by":"publisher","DOI":"10.1038\/modpathol.2011.173"},{"key":"2026060106100756000_19.6.e272914.4","first-page":"842","article-title":"Squamous cell carcinoma of the lung: an update","volume":"134","author":"Rekhtman","year":"2010","journal-title":"Arch Pathol Lab Med"},{"key":"2026060106100756000_19.6.e272914.5","first-page":"163","article-title":"Immunoreactivity for p63 in lung cancer: biological and clinical implications","volume":"194","author":"Pelosi","year":"2001","journal-title":"J Pathol"},{"key":"2026060106100756000_19.6.e272914.6","doi-asserted-by":"publisher","DOI":"10.1097\/PAS.0b013e3182a0218f"},{"key":"2026060106100756000_19.6.e272914.7","first-page":"99","article-title":"Coordinate expression of cytokeratins 7 and 20 defines unique subsets of carcinomas","volume":"3","author":"Wang","year":"1995","journal-title":"Appl Immunohistochem Mol Morphol"},{"key":"2026060106100756000_19.6.e272914.8","first-page":"659","article-title":"Immunohistochemical distinction of primary urothelial carcinoma from metastatic carcinoma in the lung","volume":"34","author":"Sangoi","year":"2010","journal-title":"Am J Surg Pathol"},{"key":"2026060106100756000_19.6.e272914.9","doi-asserted-by":"publisher","DOI":"10.2214\/AJR.10.5036"}],"container-title":["BMJ Case Reports"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/syndication.highwire.org\/content\/doi\/10.1136\/bcr-2026-272914","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,6,1]],"date-time":"2026-06-01T13:10:12Z","timestamp":1780319412000},"score":1,"resource":{"primary":{"URL":"https:\/\/casereports.bmj.com\/lookup\/doi\/10.1136\/bcr-2026-272914"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,6]]},"references-count":9,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2026,6,1]]},"published-print":{"date-parts":[[2026,6]]}},"alternative-id":["10.1136\/bcr-2026-272914"],"URL":"https:\/\/doi.org\/10.1136\/bcr-2026-272914","relation":{},"ISSN":["1757-790X"],"issn-type":[{"value":"1757-790X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,6]]}}}