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EQUINE VETERINARY EDUCATION / AE / OCTOBER 2014


30% demineralisation to occur in order to be evident radiographically (Butler et al. 2008). Also, on the post mortem radiographs, the femur was disembodied, which allowed for removal of large amounts of soft tissue, thus avoiding soft tissue super-impositioning. During radiographic examination under general anaesthesia 2 orthogonal views of the femur might have revealed osseous abnormalities such as a periosteal reaction; however, this was unfortunately not done. Notwithstanding, the authors believe that the pathological fracture only occurred on the last day at the time when the animal became severely distressed and recumbent. Alternatively, a scintigraphic examination could be


200 µm


Fig 9: Factor VIII-related antigen immunohistochemical staining of focal haemangiosarcoma in right hindlimb skeletal muscle showing marked expression in neoplastic proliferating endothelial cells (white arrow) and dilation of thin-walled vessels in an adjacent muscle bundle (black arrow).


performed without the risk of general anaesthesia in a horse with a suspected femur or pelvis fracture (Pilsworth 2011) and is likely to have yielded increased radiopharmaceutical uptake, which has been described in haemangiosarcoma of the humerus of a Clydesdale gelding (Cottle et al. 2008). Scintigraphy was not performed due to financial constraints. A traumatic incident is often implicated in the history of


horses presented for subcutaneous or muscular swelling or lameness caused by haemangiosarcoma; likewise, the ante mortem diagnosis is often incorrectly made as a haematoma (Valentine et al. 1986; Pille et al. 2004; Johns et al. 2005). Ultrasonography and fine needle aspirates are commonly unrewarding (Southwood et al. 2000; Pille et al. 2004), whereas multiple biopsies and histopathological examination might yield the diagnosis (Southwood et al. 2000; Johns et al. 2005). Due to the low level of suspicion of haemangiosarcoma as cause of severe lameness in this case no biopsy was attempted during hospitalisation. Marked bleeding has been described following biopsy (Waugh et al. 1977; Cottle et al. 2008) or fine needle aspiration (Pille et al. 2004) of haemangiosarcoma as occurred in this case. Anaemia, as was present in this case, is often the


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Fig 10: Immunohistochemical staining of neoplastic endothelial cells (white arrow) for factor VII-related antigen in the periosteum of the region of the right hindlimb femur fracture.


Discussion


The presenting complaint for horses with disseminated haemangiosarcomavaries tremendously. Inareviewof35cases, 24%werepresentedforsubcutaneousandmuscularswellingand 12%forlameness(Southwoodet al. 2000). Lungsandpleurawere most commonly affected, followed by skeletal muscle in up to 46%ofcases(Southwoodet al. 2000).Osseousinvolvementis rare and has been reported involving the equine vertebrae (Newton-Clarke et al. 1994), mandible (Southwood et al. 2000) andhumerus (Cottle et al. 2008). Tothe authors’knowledgethis is the first case report of haemangiosarcoma affecting the equine femur or of haemangiosarcoma leading to a pathological fracture in an equine long bone. Radiography on the live horse failed to show the osteopaenia seen on the post mortem radiographs of the femur. This could be explained by insufficient time elapsed for


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only consistent haematological abnormality in horses with haemangiosarcoma and is explained by blood loss and microfragmentation of the red blood cells (Waugh et al. 1977; Rebar et al. 1981; Valentine et al. 1986; Collins et al. 1994; Southwoodet al. 2000; Johns et al. 2005). In the present case, the anaemiawasbelieved tobedueto the continued intramuscular haemorrhage and haemorrhage resulting from the stab incision. Some intravascular haemolysis cannot be ruled out as serum bilirubin concentrations (Dhaliwal et al. 2004) were not measured. The carcass, however, was not icteric at the time of necropsy. The case progressed to a neutrophilic leucocytosis, which has also been reported previously (Waugh et al. 1977; Southwood et al. 2000). Increased serum alkaline phosphate activity (ALP) is


common in human cancer patients with bone metastasis (Garnero et al. 2000; Min et al. 2009). Likewise increased ALP is seen in dogs with osteosarcoma and has been correlated with the prognosis for survival (Garzotteet al. 2000). Although not measured, increased ALP in the present case was possible and could have aided in identifying the osseous involvement. Treatment in the absence of a diagnosis is supportive and


includes antimicrobial coverage, intravenous fluids, blood transfusion, corticosteroids and analgesic agents (Waugh et al. 1977; Valentine et al. 1986; Collins et al. 1994; Southwood et al. 2000; Johns et al. 2005; Reischauer et al. 2006). Isolated cases of successful surgical excision and even spontaneous resolution have been described (Pelt et al. 1972; Johns et al. 2005; Lempe et al. 2008). Interstitial brachytherapy can be used in the management of these tumours (Burks et al. 2009);


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