Hepatoblastoma with erythrocytosis in a young female horse

Abstract

A 2.5-year-old female Thoroughbred was examined because of lethargy, anorexia, and weight loss. Analysis of a CBC revealed erythrocytosis and an increase in PCV. Serum biochemical analysis revealed increases in activities of several hepatic enzymes. Ultrasonography revealed hepatomegaly and a heterogeneous appearance of the hepatic parenchyma. The horse did not improve despite supportive care, and it was euthanatized. Necropsy revealed numerous raised white to gray foci in the liver. Histologically, these foci consisted of neoplastic cells that resembled fetal hepatocytes, embryonal-type cells, and cells with features intermediate between those 2 cell types. Immunohistochemical staining revealed that hepatocytes stained strongly with anti-alpha-fetoprotein. On the basis of these results, hepatoblastoma was diagnosed. Diagnosis of hepatoblastoma is difficult, because it can appear histologically similar to other hepatic tumors, such as hepatocellular carcinomas. Definitive diagnosis requires histologic evaluation of tumor architecture and cell morphology. Immunohistochemical staining for alpha-fetoprotein in tumor cells may serve as a tumor marker but is not pathognomonic of hepatoblastoma. Paraneoplastic syndromes, such as erythrocytosis, can accompany hepatoblastoma. The prognosis for horses with hepatoblastoma is grave.

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.…”

“…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.…”

“…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.…”