Angiosarcoma

Angiosarcoma is also known as haemangioendothelioma. A low-grade epithelioid variant likewise occurs in bone.

Osseous angiosarcomas are observed in patients of all ages; the symptoms are generally local pain and swelling. Severe headaches, back pain, neurologic manifestations and fractures are among the clinical findings in this disorder. Two fundamental histologic criteria are required for the diagnosis of an angiosarcoma:

- the presence of atypical endothelial cells, and

- vascular channels with a delicate framework of reticulin fibers that may or may not anastomose. Very well differentiated angiosarcomas are difficult to distinguish from haemangiomas.

The long tubular bones, especially the femur, tibia and fibula, are the most common sites of involvement. A metaphyseal or diaphyseal location is typical. The bones of the pelvis, the skull, the ribs and the vertebrae may also be affected. Typically the lesions are multicentric, with multiple lesions within a single bone or one or more foci of tumour in multiple bones, either in a single extremity or throughout the skeleton. One of the important diagnostic signs of angiosarcoma is a regional pattern of involvement of a tubular bone of an extremity. The epithelioid variant, or epithelioid haemangioendothelioma (haemangioma), appears to be composed of a histologically distinct population of endothelial cells. This variety is occasionally multicentric but may be associated with skin lesions. The epithelioid tumours appear to be well differentiated, although they may recur after surgery. When pericytes or lymphatic endothelioblasts are involved, a malignant haemangiopericytoma or lymphangiosarcoma may occur.

On radiographs the predominant finding is osteolysis, sometimes with osteosclerosis. Thinning of the cortex, expansion of bone and periostitis are other features of angiosarcoma. Two or more lesions may involve a long segment of a single bone, or osteolysis may be seen in contiguous bones (Fig.1). In the flat or irregular bones, a similar osteolytic pattern may be demonstrated. Osteolysis affects contiguous vertebral bodies in the spine, with narrowing of the intervening intervertebral disc, which may be mistaken for infection.

DR/RB