The peculiar clinical presentation and diagnostic results of a case of widely metastatic cholangiocellular carcinoma in a Siberian Husky dog.

A six-year-old spayed female Siberian Husky dog was evaluated for acute cervical pain and ataxia, respiratory changes, and a two-month history of weight loss. Antemortem diagnostics included complete physical and neurologic examination, complete blood count, serum biochemistry, cervical and thoracic radiographs, abdominal ultrasound (AUS), and splenic and lymph node cytology. Abnormalities included C6-T2 myelopathy, mildly elevated hepatocellular enzymes, sternal lymphadenopathy, ill-defined hepatosplenic nodules, and multifocal lymphadenopathy, with concern for metastatic carcinoma cytologically. Humane euthanasia was elected, and a diagnostic necropsy was performed. Tissues were formalin-fixed and routinely processed before hematoxylin and eosin staining. Affected hepatic tissues were further evaluated by trichrome staining and immunolabeling for cytokeratins 7 and 19 (CK7 and CK19). Expanding and compressing the left lateral liver lobe was a large, infiltrative, tan-yellow, umbilicated mass. The remainder of the hepatic parenchyma contained up to 100 additional similarly appearing intrahepatic masses, and additional masses were observed grossly within the gallbladder, spleen, mesentery, urinary bladder, diaphragm, lungs, pleura, and sternal lymph nodes. Histology of the primary and metastatic lesions was consistent with cholangiocellular carcinoma (CC) with varying degrees of anaplasia, and a marked scirrhous response was confirmed with trichrome staining. The primary hepatic mass was CK19+/CK7- with immunolabeling. Cervical pain represents an atypical presentation for widely metastatic CC and is a suspected sequel of vertebral metastasis or embolic spinal disease. The primary hepatic mass was not captured by routine AUS, and immunolabeling of the primary lesion was negative for CK7 expression, highlighting challenges to antemortem diagnostics and poor cellular differentiation, respectively.