Hepatoblastoma with erythrocytosis in a young female horse.

This research article details a case of a young horse diagnosed with hepatoblastoma, a rare liver tumor, accompanied by erythrocytosis. The disease, despite supportive care, leads to the eventual euthanization of the horse due to lack of improvement and grave prognosis.

Case Description

• The study begins with a case of a 2.5-year-old female Thoroughbred horse exhibiting signs of lethargy, anorexia, and weight loss. Upon analysis of a complete blood count (CBC), erythrocytosis (an excessive amount of red blood cells in the blood) was detected, alongside an increased packed cell volume (PCV). Additionally, abnormal levels of several hepatic enzymes were observed in the serum biochemical analysis, indicating potential liver disease.
• Ultrasonography showed hepatomegaly (an enlarged liver) and a heterogeneous appearance of the hepatic parenchyma, further suggesting liver pathology. Despite supportive care, the horse’s condition worsened.

Necropsy and Histologic Findings

• Upon euthanization and necropsy of the horse, many raised white to gray foci were observed in the liver. Histological examination of these foci revealed the presence of neoplastic (abnormal and uncontrolled cell growth) cells that resembled fetal hepatocytes, embryonal-type cells, and cells with characteristics intermediate between these two types.
• Immuno-histochemical staining showed that the hepatocytes stained strongly with anti-alpha-fetoprotein, a protein usually found in the liver of fetuses. This unusual staining pattern supported the diagnosis of hepatoblastoma – a rare type of liver cancer often seen in children and, evidently, young animals.

Challenges in Diagnosis

• Diagnosing hepatoblastoma is complex due to its histological similarity to other hepatic tumors, such as hepatocellular carcinomas. Definitive diagnosis demands careful histologic assessment of the tumor architecture and cell morphology.
• Despite the presence of alpha-fetoprotein in the tumor cells serving as a potential tumor marker, it is not completely conclusive of hepatoblastoma since this protein can be seen in several other malignant conditions.

Association with Paraneoplastic Syndromes

• Erythrocytosis, as observed in the young female Thoroughbred, is identified as a potential paraneoplastic syndrome, a disease or symptom that is the consequence of the presence of cancer in the body, that can accompany hepatoblastoma.
• The poor prognosis in horses with hepatoblastoma is highlighted, with the current literature hinting towards a grave outcome in such cases.