{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,12]],"date-time":"2026-06-12T04:59:11Z","timestamp":1781240351284,"version":"3.54.1"},"reference-count":38,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,6,12]],"date-time":"2026-06-12T00:00:00Z","timestamp":1781222400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Oncol."],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Invasive lobular carcinoma (ILC) is a distinct breast cancer subtype with a characteristic infiltrative growth pattern linked to loss of E-cadherin. GI metastases may clinically and histologically mimic primary GI malignancies, creating significant diagnostic pitfalls.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Case presentation<\/jats:title>\n                    <jats:p>\n                      A 52-year-old woman with\n                      <jats:italic>de novo<\/jats:italic>\n                      metastatic, grade 1, luminal A ILC (ER+\/PR+, HER2 0; Ki-67 5%) diagnosed in 2022 achieved durable disease control with systemic therapy and maintenance ribociclib plus ovarian suppression. In late 2025, she developed progressive epigastric discomfort and rising tumour markers. Gastroduodenal endoscopy demonstrated erythematous gastric mucosa with focal whitish areas. Biopsies showed diffuse-type adenocarcinoma with signet ring morphology, initially interpreted as primary gastric cancer. Expert review with comparative pathology and extended immunohistochemistry demonstrated GATA3 and TRPS1 positivity, strong ER\/PR expression, CDX2 negativity, and loss of E-cadherin, supporting gastric metastasis from ILC. Despite no clear radiologic progression on CT, symptomatic gastric involvement and weight loss prompted initiation of second-line weekly paclitaxel.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>Signet ring morphology in gastric biopsies is not pathognomonic for primary gastric carcinoma. In patients with current or prior ILC, an IHC panel incorporating breast-lineage markers (e.g., GATA3, TRPS1) and GI markers (e.g., CDX2, CK20), alongside E-cadherin status, is pivotal to avoid misdiagnosis, inappropriate surgery, and delay of systemic therapy.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fonc.2026.1852381","type":"journal-article","created":{"date-parts":[[2026,6,12]],"date-time":"2026-06-12T04:46:54Z","timestamp":1781239614000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Case Report: Not all signet rings are of gastric origin: a case of lobular breast carcinoma metastatic to the stomach"],"prefix":"10.3389","volume":"16","author":[{"given":"Amalia A.","family":"Sofianidi","sequence":"first","affiliation":[{"name":"Eugenideio Hospital, National and Kapodistrian University of Athens","place":["Athens, Greece"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Constantinos","family":"Papadimitris","sequence":"additional","affiliation":[{"name":"Eugenideio Hospital, National and Kapodistrian University of Athens","place":["Athens, Greece"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Maria","family":"Papanikolaou","sequence":"additional","affiliation":[{"name":"First Department of Pathology, Laikon General Hospital, Medical School, National and Kapodistrian University of Athens","place":["Athens, Greece"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eleftheria","family":"Lakiotaki","sequence":"additional","affiliation":[{"name":"First Department of Pathology, Laikon General Hospital, Medical School, National and Kapodistrian University of Athens","place":["Athens, Greece"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Penelope","family":"Korkolopoulou","sequence":"additional","affiliation":[{"name":"First Department of Pathology, Laikon General Hospital, Medical School, National and Kapodistrian University of Athens","place":["Athens, Greece"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Meletios-Athanasios","family":"Dimopoulos","sequence":"additional","affiliation":[{"name":"Department of Clinical Therapeutics, \u201cAlexandra\u201d General Hospital, Medical School of National and Kapodistrian University of Athens","place":["Athens, Greece"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Maria","family":"Kaparelou","sequence":"additional","affiliation":[{"name":"Department of Clinical Therapeutics, \u201cAlexandra\u201d General Hospital, Medical School of National and Kapodistrian University of Athens","place":["Athens, Greece"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,6,12]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","DOI":"10.1177\/03000605241233988","article-title":"Gastric metastasis from breast cancer: Five cases and a single-institutional review","volume":"52","author":"Cheng","year":"2024","journal-title":"J Int Med Res"},{"key":"B2","doi-asserted-by":"publisher","DOI":"10.1002\/1097-0142(20001201)89:11<2214::aid-cncr9>3.0.co;2-d","article-title":"Clinical presentation, endoscopic features, and treatment of gastric metastases from breast carcinoma","volume":"89","author":"Taal","year":"2000","journal-title":"Cancer"},{"key":"B3","article-title":"Metastatic patterns of invasive lobular versus invasive ductal carcinoma of the breast","volume":"114","author":"Borst","year":"1993","journal-title":"Surgery"},{"key":"B4","doi-asserted-by":"publisher","DOI":"10.1038\/bjc.1997.523","article-title":"E-cadherin inactivation in lobular carcinoma in situ of the breast: An early event in tumorigenesis","volume":"76","author":"Vos","year":"1997","journal-title":"Br J Cancer"},{"key":"B5","article-title":"Signet ring variant of lobular carcinoma of the breast: A clinicopathologic and immunohistochemical study","volume":"6","author":"Raju","year":"1993","journal-title":"Mod Pathol Off J U S Can Acad Pathol Inc"},{"key":"B6","doi-asserted-by":"publisher","DOI":"10.1016\/j.critrevonc.2026.105170","article-title":"Signet-ring cell cytomorphology in breast cancer: Unveiling the overlooked","volume":"220","author":"Su","year":"2026","journal-title":"Crit Rev Oncol Hematol"},{"key":"B7","doi-asserted-by":"publisher","DOI":"10.1245\/ASO.2005.03.030","article-title":"Breast cancer: Presentation and intervention in women with gastrointestinal metastasis and carcinomatosis","volume":"12","author":"McLemore","year":"2005","journal-title":"Ann Surg Oncol"},{"key":"B8","doi-asserted-by":"publisher","DOI":"10.15403\/jgld.2014.1121.274.gas","article-title":"Gastric metastasis mimicking linitis plastica 20 years after primary breast cancer. 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