Hemangiosarcoma (hemangioendothelioma) is a malignant mesenchymal tumor arising from vascular endothelium which form irregular anastomosing vasoformative channels occurring most frequently in dogs than in other species and with a high fatality rate¹. Since the tumor arises from vascular endothelium it can develop in any site where blood vessels are present. Hemangiosarcoma is an uncommon neoplasm in domestic animals, being more common in dogs than in cats. On perusal of literature only few cases have been documented in wild felines. Five cases of hemangiosarcoma were documented in three tigers and two lions during post-mortem examinations²; one case in spleen of lion^3,4 and one case in liver and lung of an Asiatic lion⁵. The most commonly involved organs are spleen, lungs, heart, liver and pancreas^2,3,4. Both visceral and non-visceral forms of Hemangiosarcoma have been described in dogs, with the visceral form more commonly being identified in wild felids.^2,5,6 The present case describes an incidental finding of both visceral and non-visceral form of hemangiosarcoma in a tigress and its pathological features.

A BBP born Bengal tigress named ‘Bhavani’ aged about 4 years was presented to Wild Animal Disease Diagnostic Laboratory, Bannerghatta National Park near Bengaluru for Postmortem examination after prolonged illness for several months after she developed growing mass in the left forelimb. On external examination of the carcass, the visible buccal and conjunctival mucosa appeared bleached, with presence of ticks on the body. A hard swelling that was roughly spherical with 4-5 cm diameter was observed attached to the skin in the left forelimb in the humerus region. On internal examination, subcutaneous tissue was dry and pale, pericardium was filled with serosanguinous fluid, lung was enlarged and congested with presence of large number of encapsulated oval to circular lesions of varying sizes (0.5cm to 3-4 cm in diameter) throughout the lung parenchyma (Fig. 1). Lesions were severely congested and appeared prominently raised above the surface. Liver looked enlarged, congested and was imbibed with bile. Spleen was enlarged, congested and showed presence of 6-7 of encapsulated lesions of varying size from 0.5cm to 3-6 cm in diameter similar to the ones found in the lungs (Fig 2.) These lesions also had circumferential area that was congested and raised. The encapsulated mass adjoining to the left humerus bone was found to be firm and brick red in color. Humerus bone adjacent to the tumorous mass showed decalcification and necrotic changes. The bone was very soft and was easily sliced by the knife.

Impression smears from the lesions were collected and fixed with methanol and stained using giemsa staining. The representative samples from the growths in bone, lungs and spleen were collected and fixed in 10% NBF for histopathological examination. The samples were processed by routine paraffin embedding technique, sectioned at approximately 4-5μ thickness and stained with routine haematoxylin and eosin method⁷.

In the present case, tumor mass was found on lung, spleen and in humerus region with no clear indication of primary locus and secondary spreading in these organs. Hemangiosarcomas may be solitary, multifocal within an organ, or widely disseminated at presentation. When metastases are widespread, the primary tumor site may be difficult to determine, and a multicentric origin is a possibility. Grossly, the encapsulated mass found on lungs and spleen on incision showed red cavernous tissue. Similar finding in liver of lion has been reported⁵. Giemsa stained impression smears revealed presence of oval to fusiform mesenchymal cells that contained small punctate cytoplasmic vacuoles with high nuclear-to-cytoplasmic ratios, oval nuclei with coarse chromatin, and prominent multiple nucleoli. The cytology smear also showed large number of inflammatory cells.

The tumor can arise in any site of the body. However, the most common primary sites are spleen, lung, skin/subcutis, right atrium and liver^2,5,6. The most predisposed tissues to metastasis are the lungs, liver, heart, skin, skeletal muscles, kidney, brain and bones⁸. However, in the present case no growths were seen in organs other than bone, spleen and lung. Hemangiosarcoma is the most prevalent splenic neoplasm and this is considered as the predilection site for primary incidence in dogs. The average time of survival with a metastatic lesion being detected or not is about four to six months. In domestic cats, the major sites of hemangiosarcoma included abdominal cavity (48.5%), subcutaneous tissue (42%), thoracic cavity (6.5%), and nasal cavity (3%)⁸.

Histopathological examination of the mass from lung and spleen revealed sheets of fast multiplying anaplastic endothelial cells. These proliferative endothelial cells showed hyperchromasia, pleomorphism (spindle-shaped to polygonal to ovoid morphology), increased nuclear to cytoplasmic ratio and increased mitotic proliferation. Fibrous connective tissue stroma was prominent with micro thrombi formation. It also showed formation of vascular spaces (cavernous and capillary) filled with erythrocytes. Blood spaces were formed due to endothelial proliferation. In few areas, stroma between the clefts was devoid of cells, darkly eosinophilic and hyaline like. Histopathologically, the growth analyzed here had the similar features as previously reported^2,8. Based on the pathological features, the tumor mass was diagnosed as a case of Hemangiosarcoma.

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