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To identify common diagnostic pitfalls and define practical diagnostic criteria, we retrospectively reviewed 24 suspected CCA cases across 16 species submitted to Johns Hopkins University between 1986 and 2024. Twelve cases were confirmed as CCA, 2 were unclassified, and 10 were reclassified as biliary adenoma, biliary hamartoma, polycystic liver disease, primary neuroendocrine tumor, or metastatic adenocarcinoma based on histology and immunohistochemistry (cytokeratin, synaptophysin). From recurring diagnostic patterns, we developed a diagnostic flowchart emphasizing mass effect, growth pattern, architectural pattern (cystic vs. solid), features of malignancy, and immunohistochemical criteria to aid in stepwise interpretation of proliferative ductular lesions. Furthermore, confirmed CCA cases aligned with large- and small-duct subtypes described in human pathology. Collectively, our cases underscore both the diagnostic challenges and shared histomorphologic and immunohistochemical characteristics across species within the spectrum of biliary proliferative disorders.<\/jats:p>","DOI":"10.1177\/10406387261450615","type":"journal-article","created":{"date-parts":[[2026,6,18]],"date-time":"2026-06-18T04:16:43Z","timestamp":1781756203000},"page":"1323-1329","update-policy":"https:\/\/doi.org\/10.1177\/sage-journals-update-policy","source":"Crossref","is-referenced-by-count":0,"title":["Interspecies comparative features of cholangiocarcinoma and histologic mimics"],"prefix":"10.1177","volume":"38","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7169-8504","authenticated-orcid":false,"given":"Katti R.","family":"Crakes","sequence":"first","affiliation":[{"name":"Departments of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hannah M.","family":"Stephen","sequence":"additional","affiliation":[{"name":"College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kiyoko","family":"Oshima","sequence":"additional","affiliation":[{"name":"Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"John G.","family":"Trupkiewicz","sequence":"additional","affiliation":[{"name":"Departments of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5183-3980","authenticated-orcid":false,"given":"Eunju April","family":"Choi","sequence":"additional","affiliation":[{"name":"Department of Pathology, Microbiology, and Immunology, University of California\u2013Davis, School of Veterinary Medicine, Davis, CA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6666-6548","authenticated-orcid":false,"given":"Cory","family":"Brayton","sequence":"additional","affiliation":[{"name":"Departments of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"179","published-online":{"date-parts":[[2026,6,17]]},"reference":[{"key":"e_1_3_3_2_2","first-page":"12","article-title":"Causes of mortality in sloth bears (Melursus ursinus) housed in U.S. zoos","volume":"6","author":"Anderson K","year":"2018","unstructured":"Anderson K, et al. 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