The term hamartoma refers to focal disordered overgrowth of mature tissue that is indigenous to the organ involved [1]. Vascular hamartomas may occur at any site in the body. Most hamartomas are present at birth and their growth is coordinated with that of the surrounding tissue. Mesenchymal (largely vascular) hamartomas of the human liver, though rare, are a distinct clinicopathological entity, occurring primarily in infants and young children and seldom in adults [2–6]. Hamartomas in cattle have also been described primarily in calves, young animals and rarely in adults. In calves, hamartoma of the bile ducts [7], lungs [8], vagina [9], testicle [10], smooth muscle of the abomasum [11] and gingiva [12–15] has been reported. In adult cattle, hamartoma of the liver [16], ovary [17] and heart [18] has been described. Hamartoma of the liver in human fetuses and children manifests clinically as abdominal enlargement. However, in cattle, hamartoma has not been diagnosed in vivo and is usually an incidental finding at necropsy or slaughter [16]. The goal of this case report was to describe the ultrasonographic findings in a six-year-old Swiss Braunvieh cow with hamartoma of the liver.

The cow was referred to our clinic because of regurgitation, which will not be discussed in this report. Abdominal ultrasonography using a 5.0 MHz-convex transducer revealed an abnormally large number of hypoechogenic blood vessels in the liver parenchyma (Figure 1) and a thrombus in a vein, which was thought to be the right hepatic vein (Figure 2). The caudal vena cava had a normal triangular shape in cross section, and the portal vein had typical stellate ramifications. Neither of these two vessels were dilated, and the liver appeared normal in size. Abdominal effusion was not seen. The activities of gammaglutamyl transferase (γ-GT), aspartate aminotransferase (AST), glutamate dehydrogenase (GLDH) and sorbitol dehydrogenase (SDH) and the concentration of bilirubin were within the reference ranges of the Clinical Laboratory, Vetsuisse Faculty, University of Zurich (γ-GT 25 U/l, reference range 13 - 32 U/l; AST 40 U/l, reference range 30 - 103 U/l; GLDH 13.3 U/l, reference range 4 - 18 U/l; SDH 5.2 U/l, reference range 4.0 - 7.4; bilirubin 4.2 μmol/l, reference range 1.5 - 6.5 μmol/l). The cow was euthanased because of regurgitation. Postmortem examination revealed a perioesophageal abscess, which was likely the cause of regurgitation, moderate ascites and two abomasal ulcers. The right hepatic lobe had a cavernous, poorly delineated, non-encapsulated mass measuring 10 cm in diameter. The cut surface of the lesion was sponge-like (Figure 3) and contained extremely dilated blood vessels, one of which was occluded with a branching red thrombus (Figure 4). Blood vessels in the remainder of the liver were also markedly dilated. The gallbladder contained numerous Dicrocoelium dendriticum flukes. Histological examination of H&E-stained sections of the right liver lobe revealed that the parenchyma was obliterated by a non-encapsulated, cavernous lesion consisting of well-differentiated, blood-filled venous and arterial vascular spaces. The endothelial cells were immunohistochemically positive for factor VIII related antigen. These spaces were separated by a well-differentiated connective tissue arranged in tightly-packed bundles of spindle-shaped cells, which varied in width and were irregularly arranged (Figure 5, 6). In some of the dilated vessels, the lamina muscularis had areas of atrophy as well as hypertrophy (Figure 7). A well-organised red thrombus was found in one of the blood vessels. Focal haemorrhages, regenerative nodules with partially degenerated hepatocytes, accumulation of degenerated neutrophils and marked proliferation of bile ducts were seen at the margin of the lesion. Elsewhere in the liver, there was severe portal fibrosis and bile duct proliferation attributable to infestation with Dicrocoelium dendriticum. Based on the histological findings, vascular hamartoma of the liver with thrombosis was diagnosed.

Hamartoma of the liver is rare in mammals. In cattle, there is only one report, which described the postmortem diagnosis of liver hamartoma in eight healthy slaughter cattle [16]. Liver hamartoma has been reported in an equine fetus [19] and three dogs [20–22]. In contrast to human beings, liver hamartoma in cattle does not appear to be clinically significant. The bovine cases described were incidental findings during post-slaughter inspection [16]. In the present case report, the liver hamartoma was also a coincidental finding during work-up of a regurgitation problem, in which routine ultrasonography revealed a liver lesion. The ultrasonographic appearance of the lesion was confusing because it did not resemble anything we had seen in the past 20 years. However, the findings were similar to multicystic lesions described for liver hamartoma in human medicine [2, 4–6]. In our case, it was not clear initially whether the dilated vessels were blood vessels or bile ducts. The differential diagnosis included dilatation of hepatic vasculature attributable to right-sided cardiac insufficiency or thrombosis of the caudal vena cava; cholestasis and neoplasia were other possible rule-outs. Right ventricular heart failure was ruled out because the cow had a normal heart rate and no jugular distension. The venous thrombus suggested thrombosis of the caudal vena cava because septic thrombi have been described in the caudal vena cava [23] as well as in the hepatic veins [24]. Thrombosis of the caudal vena cava was ruled out because in our experience, this vein is oval to circular in cross-section when dilated [25]. In addition, the pattern of multiple dilated vessels had not been seen previously in cases with thrombosis of the caudal vena cava. The red thrombus found in our patient was likely attributable to poor venous blood flow or blood stasis. Its red colour was due to a high proportion of erythrocytes and relatively few platelets [26]. Similar thrombi were found in four of eight hamartomas in cattle [16]. The ascites seen in our patient was due to portal hypertension [21]. The ultrasonographic findings of the liver were uncharacteristic of cholestasis [25] or liver tumours [27]. The activities of liver enzymes and concentration of bilirubin were also normal, which did not support a diagnosis of cholestasis or liver tumour. A biopsy may have provided an in-vivo diagnosis, but euthanasia was elected for other reasons. However, it is questionable whether biopsy is indicated in a suspected vascular tumor. The findings of this case report provide important reference data for the diagnosis of liver hamartoma in cattle.

In cows with a greater than normal number of hypoechogenic blood vessels in the liver parenchyma, the differential diagnosis should include vascular hamartoma. To our knowledge, this is the first description of the ultrasonographic findings of vascular hamartoma of the liver in cattle. Vascular hamartoma of the liver must be part of the diffferential diagnosis in cows with dilated liver vessels, normal activities of liver enzymes and a normal concentration of bilirubin. The case reported broadens the spectrum of liver diseases and the ultrasonographic findings of the liver in cattle.

Consent was obtained from the owner of the cow for publication of this case report and any accompanying images.