Intrahepatic mucinous cholangiocarcinoma with recurrent colic in a horse case report and literature review of cholangiocarcinoma in horses

Abstract

A 17-y-old Arabian mare was presented to the Auburn Large Animal Veterinary Teaching Hospital with a long-term history of intermittent mild recurrent colic that responded to medical treatment. CBC revealed mild lymphopenia; serum biochemistry findings were of increased gamma-glutamyl transferase and creatine kinase activities, hyperferremia, hyperglycemia, hypomagnesemia, and hypokalemia. Abdominocentesis was compatible with low-protein transudate. Due to the progression and duration of clinical signs, the owner elected euthanasia. Postmortem examination and histopathology confirmed a cholangiocarcinoma. The neoplastic cells were arranged in large cysts containing lakes of mucin that comprised 90% of the tumor volume; thus, a mucinous variant was determined. The neoplastic cells had strong cytoplasmic immunolabeling for cytokeratin 19 and lacked immunolabeling for hepatocyte paraffin 1, supporting bile duct origin. Cholangiocarcinomas are infrequent tumors in horses with nonspecific and slow progressive clinical signs, including recurrent colic. Mucinous cholangiocarcinomas are seldom reported in veterinary medicine and, to our knowledge, have not been reported previously in horses.

Keywords: HepPar1; cytokeratin 19; horses; mucinous cholangiocarcinoma; neoplasia.

Figure 1.

Intrahepatic mucinous cholangiocarcinoma in a 17-y-old Arabian mare. A. White-tan, raised, 0.5–1-cm nodules in the hepatic lobes (arrowheads), and a 3-cm nodule (dashed square) in the right hepatic lobe. Inset: on cut surface of the nodule, cavitations are filled with yellow to pale-brown secretion. B. Within the left lateral, medial, and quadrate hepatic lobes, the nodules are cavitated, filled with abundant dark-green, mucoid, secretion. C. In the liver parenchyma, numerous cystic, paucicellular, infiltrative, non-encapsulated, neoplastic nodules arise from the bile ductular epithelium. Neoplastic cells form papillary projections and fronds, delineated by columnar cells, with mucoid cellular differentiation and supported by a fibrous stroma. H&E. Bar = 200 µm. D. The cysts and cells are filled with amorphous, purple, laminated mucus that comprises 90% of the neoplasm volume. Alcian blue mucicarmine stain. Bar = 200 µm. E. Neoplastic cells have strong cytoplasmic immunolabeling for CK19. Normal bile ducts are internal positive controls (arrow). Bar = 100 µm. Inset: magnified immunostaining. Bar = 20 µm. F. Neoplastic cells lack immunolabeling for HepPar1. Hepatocytes (asterisk) are the internal positive control. Bar = 100 µm.