Angiosarcoma of the breast is a very rare type of breast cancer that develops from abnormal cells in the walls of blood vessels or lymphatic vessels. Although it is difficult to be sure how often it occurs, probably less than 1 in 10,000 women will ever develop the condition, whereas 1 in 9 women will develop the more common type of breast cancer at some stage during their life.

There are two types of angiosarcoma of the breast. The first type, sometimes called primary angiosarcoma of the breast, has no known cause. It tends to occur in younger women in their 30s or 40s. The first sign may be a painless lump within the breast or the breast may become bigger. Some reddish or purplish discoloration of the breast may also be noticeable.

The second type is sometimes called secondary angiosarcoma of the breast. It occurs as a late complication of treatment for breast cancer, particularly radiotherapy, although there have also been cases related to surgery or to swelling of the arm and breast tissues after surgery (lymphoedema).

Angiosarcoma after breast radiotherapy is very rare and probably less than 1 in every 7000 women who have breast radiotherapy will go on to develop the condition. When it does occur it usually appears about 7 or 8 years after radiotherapy (although intervals of anywhere from 2 to 15 years have been reported). It is usually found in women in their 60s or 70s. The cancer usually appears on the skin of the breast or in the scar from previous breast surgery and may cause generalised redness or patches of red, blue or purple discoloration on the skin.

Wherever possible surgery is the first line of treatment for both types of angiosarcoma, and usually involves a mastectomy. As it is rare for angiosarcoma of the breast to spread to lymph nodes, it is not usually necessary to remove the lymph nodes. Chemotherapy may be given before or after surgery or if the cancer comes back. On occasion immunotherapy drugs such as interferon are used. Women with primary angiosarcoma of the breast may also be offered radiotherapy.

Angiosarcomas can spread to other parts of the body, most often to the lungs, and this means they cannot always be cured. Overall the figures suggest that about 6 out 10 women who develop the condition will survive for more than 5 years after their cancer is discovered.