Case 4 - 170526-4

Approximately 1.5-year-old, cat.

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Two sections of liver are represented on this slide. Approximately 80% of one section is swollen and pale due to extensive coagulative necrosis. Both section have a markedly increased number of biliary profiles, which expand portal regions. These consist of immature to well-differentiated bile ducts that are variably sized, tortuous and irregularly shaped, with mild to moderate dilatation of the lumina. They are separated by moderately dense collagenous stroma and occasionally breach the portal fibrous rim. Small numbers of lymphocytes Infiltrate these same regions, dissecting between these proliferative biliary profiles. Biliary epithelium is monomorphic with minimal anisocytosis or anisokaryosis and no identified mitotic figures. The ducts are lined by a single layer of cuboidal epithelium. Occasionally, biliary lumina contain scant, wispy, lightly eosinophilic debris.

Clusters of hematopoietic precursor cells are scattered throughout the hepatic parenchyma, but they are particularly associated with periportal regions. Histiocytic cells lining sinusoids (presumed Kupffer cells) often contain a small amount of gold-brown, granular, cytoplasmic pigment and some canaliculi are plugged by bile.

There is variation in distance between portal triads and central veins and decreased distances are common, indicating lobular atrophy. The capsule of the liver is multifocally thickened by fibrous connective tissue, occasional scant fibrin mats admixed with a few lymphocytes, and hyperplastic mesothelial cells.

This slide also contains sections of heart, lung and lymph node. Lesions in these tissues are minimal and are unrelated to the liver disease. However, the medullary sinuses of the lymph node do have a moderate accumulation of macrophages with greenish-tan, intracytoplasmic pigment suggestive of lipofuscin.

No special stains. Immunohistochemistry - N/A.

Severe, generalized, portal biliary dysplasia with moderate, portal fibrosis, mild lymphocytic periportal hepatitis, multifocal extramedullary hematopoiesis, and lobular atrophy

Severe, cute, regionally extensive, hepatic necrosis with mild, multifocal, fibrinous, lymphocytic serositis

Biliary dysplasia is not a common condition and, in human literature, may be considered a pre-neoplastic change associated with cholangiocarcinoma. In this case, a diagnosis of biliary dysplasia was given based on the increased number of ductular profiles, variable ductular dilation, large and irregularly shaped ducts with occasional mild piling up of epithelial cells, and luminal infolding.

Some people reviewing the slides thought that it was difficult to determine if this was a primary biliary dysplasia or a lesion occurring secondary to some other insult. Platynosomum fastosum has been associated with biliary dysplasia in cats. However, biliary flukes would be expected to result in more significant cholangiohepatitis than was evident in this case.

The large area of necrosis was also a significant point of discussion, and how it related to the biliary dysplasia was uncertain. Such a large region of coagulative necrosis would strongly suggest infarction. The dual blood supply of the liver provides it with significant resistance to infarction. As a result, infarction would suggest a major vascular occlusion with anemia (as suggested by the hematopoiesis) or a torsion that would block both the portal veins and hepatic arteries, or branches thereof. Unfortunately, no additional information was available for this case.

Fleming K, Boberg K, Glaumann H, Clausen P. 2001. Biliary dysplasia as a marker of cholangiocarcinoma in primary sclerosing cholangitis. Journal of hepatology. 34(3):360-365.