Erythrocytosis and pleural effusion associated with a hepatoblastoma in a Thoroughbred yearling

Abstract

A 10-month-old Thoroughbred filly was presented with a 2-month history of recurrent fever and pleural effusion. Major clinical findings were pyrexia and congested mucous membranes. Clinical pathology tests revealed an erythrocytosis, hyperfibrinogenaemia and hyperglobulinaemia. Pleural fluid was seen on ultrasonographic examination of the thorax and analysis of a thoracocentesis sample indicated a lymphocytic, modified transudate. A transtracheal aspirate was normal. The erythrocytosis persisted despite IV fluid therapy. Arterial blood gas analysis and bone marrow aspirate were normal. These findings were indicative of secondary inappropriate erythrocytosis. Ultrasonographic examination of the abdomen showed a large encapsulated heterogeneous mass in the left lobe of the liver. Histopathological evaluation of a biopsy of the mass was indicative of a hepatic carcinoma. The filly was euthanased and necropsy confirmed the presence of a hepatic tumour with no evidence of systemic metastasis. Further histopathological evaluation confirmed the tumour to be an embryonal macrotrabecular epithelial-type hepatoblastoma, a type of hepatoblastoma that has not previously been reported in a horse.

Equine Primary Liver Tumors: A Case Series and Review of the Literature

“…3,8,13,21,22,27,29 Traumatic rupture of these tumors as a result of dystocia was reported in equine neonates 22 and have also been reported in humans. 34 Juvenile horses frequently presented with a nonspecific history of lethargy, fever, inappetence, weight loss, diarrhea, and mucous membrane congestion.…”

“…34 Juvenile horses frequently presented with a nonspecific history of lethargy, fever, inappetence, weight loss, diarrhea, and mucous membrane congestion. 3,8,13,21,29 Icterus, dyspnea, and pleural effusion were among the more specific signs noted. 3 Laboratory findings were indicative of inflammatory conditions, liver dysfunction or hepatocellular necrosis, and erythrocytosis.…”

“…5,10,12,16,38 Primary equine liver tumors are rare, with only 17 cases reported, of which 9 were classified as HB (Table 1). 3,4,8,13,18,19,21,22,24,27,29,32,33,35 Other reports of primary hepatic tumors in fetuses and juvenile horses included mixed hamartoma, 33 mesenchymal hamartoma, 4 and HCC. 18,32 In mature horses, cholangiocellular carcinoma 24 and combined HCC and cholangiocarcinoma have also been diagnosed ( Table 2).…”

“…16 The number of reports of equine HB is too low to make generalizations, but the primary tumor was in the left liver lobe in 6 out of 9 equine HB cases. 3,8,13,21,22,27,29 Ultrasonographically, human HB typically appeared as a lobulated, vascular, solid mass with calcification and hypoechoic areas that may have indicated necrosis or hemorrhage. 34 Metastases to abdominal lymph nodes are considered rare in HB but not in HCC.…”

“…12 Hepatoblastoma features commonly reported in horses included hepatomegaly, single to multifocal masses with heterogeneous echogenicity, encapsulation, and cavitation. 3,8,13 Hepatoblastomas in humans occasionally elaborate cytokines or hormones resulting in polycythemia, hypoglycemia, thrombocytosis, 2,15,25 precocious puberty and virilization, 26 osteoporosis, 1 or opsoclonus-myoclonus syndrome. 39 Some similar paraneoplastic effects such as polycythemia 3,13,21 and persistent hypoglycemia 13 have also been described in horses.…”