Hemangiosarcoma is a rare malignant neoplasm of vascular origin. It consists of atypical endothelial cells and undifferentiated sarcoma cells, proliferates rapidly, grows invasively and is associated with a poor prognosis.
About 75% of HS arise in the skin or soft tissues, with other organs being affected as follows: liver, 6%; heart, 5%; bones, 4%; spleen 3% .
Hematogenous spread is common, and metastases most frequently develop in the lungs. Accordingly, patients may present with signs of lung cancer.
Fine-needle aspiration biopsy and histopathological analysis of obtained specimens will reveal characteristic features. On the one hand, there are epithelioid cells lining small cavities that distantly resemble blood vessels. On the other hand, spindle-shaped sarcoma cells are present. They are generally arranged in strands and form the backbone of vessel-like structures. With regards to nuclei, aberrant mitotic figures are frequently observed . There may be necrotic foci. Antibodies directed against vascular markers like CD31, CD34, and FLI1 may be used for immunohistochemical analyses to corroborate histological findings.
While this approach is feasible in case of superficial HS, a more extensive preparation is required to obtain tumor samples from other sites. Here, imaging techniques have to be applied first in order to confirm the presence of a local mass and to obtain information regarding its accessibility  .
Hemangiosarcoma (HS) is a rare malignant neoplasm originating from mesenchymal tissue, namely from endothelial cells. This neoplasm is often described as a spongy tumor composed of dysfunctional blood vessel cells that are positioned together by undifferentiated sarcoma cells arranged in strands. The tumor is well supplied with blood. It differs largely from its benign counterpart, the hemangioma; HS generally affect the elderly, grow rapidly and invasively, and metastasize early. Hemangioma is typically diagnosed in neonates, grows slowly and resolves spontaneously.
HS primarily develop in the skin, in superficial or deep soft tissues, but they may also affect the liver, spleen, heart, or any other organ . Little is known about the disease' etiology, but patients suffering from chronic lymphedema as well as those who received radiation therapy are known to be predisposed for HS . It has been suggested that the growing number of patients exposed to therapeutic radiation accounts for the observed increase in HS incidence rates.
Of note, HS is a rather common diagnosis in veterinary medicine. Dogs are most frequently affected, but this tumor is also diagnosed in other species of domestic and wild animals. In order to avoid confusion between human and non-human HS, the term angiosarcoma is sometimes preferred for the disease of men. In any case, research concerning human HS is complicated by the low incidence of the disease. This does not apply to veterinary medicine and research; efforts made in this discipline may eventually allow the design of target-oriented studies in humans.