Angiosarcoma is a rare, aggressive, malignant tumor of vascular or lymphatic vessels. These tumors can be seen as a solitary finding or secondary to long-standing lymphedema, such as after radiation therapy or an axillary or inguinal lymph node dissection. This latter form tends to occur years after the radiation or surgical procedure. Soft tissue sarcomas are very rare and make up a small percentage of all malignancies reported.
Clinical Findings: Angiosarcomas are most common in the older male population. They have no race predilection. The tumors most commonly arise in the head and neck region and can manifest in many fashions. They often appear as a red to purple plaque with ill-defined borders. They can often look like a bruise, and the diagnosis can be delayed. The tumor continues to expand, forms satellite foci of involvement, and eventually ulcerates and bleeds. For some reason, the scalp and face of older men are most commonly involved. The tumor has a propensity to involve sun-exposed areas of the face and scalp. The tumors typically show an aggressive growth pattern and have a tendency to metastasize early in the course of disease.
Angiosarcomas can also arise in regions of previous long-standing lymphedema caused by radiation exposure or surgical procedures. Any procedure that can result in abnormal lymphatic drainage can lead to chronic lymphedema. It is believed that long-standing lymphedema can result in the development of angiosarcoma. Common surgical procedures that cause chronic lymphedema are radical mastectomies and lymph node dissections of the axilla or groin after a diagnosis of lymph node involvement by breast cancer or mela- noma. Angiosarcomas arising in areas of chronic lymphedema were first described by Stewart and Treves and have been given the eponym Stewart-Treves syndrome. This type of angiosarcoma is highly aggressive and portends a poor outcome. The Stewart-Treves type of angiosarcoma has been reported most commonly in women who have undergone radical mastectomy or lymph node dissection for treatment of breast cancer. After years of chronic lymphedema in the ipsilateral limb, the patient may develop a reddish, bruise-like area on the limb. This area slowly enlarges and develops plaque-like areas or nodules within the affected region. At this point, the diagnosis is often entertained, and the diagnosis is made with a skin biopsy. These tumors tend to be large at diagnosis, which most likely accounts for the poor prognosis.
Radiation-induced angiosarcomas may occur at the site of the radiation therapy or as a result of long-standing chronic lymphedema if the radiation therapy interrupts the lymphatic drainage. These tumors also tend to be diagnosed after they have become quite large, and this portends a poor prognosis. These tumors tend to occur 4 to 10 years after the initial radiation therapy.
Pathogenesis: Angiosarcomas are soft tissue tumors that are derived from the endothelial lining of small blood or lymphatic vessels. Some tumors are found to have elevated levels of vascular endothelial growth factor (VEGF), which is critical in the regulation of vessel growth. Other potential players in the pathogenesis of this tumor are mast cells, which cause an increase in stem cell factor; Fas and Fas ligand expression; and lack of the vascular endothelial cadherin protein. All of these factors may interact in an unknown way to induce tumorigenesis. The exact mechanism of formation of angiosarcoma is unknown. Radiation-induced angiosarcoma may result from a direct mutagenic effect of the radiation on the endothelial DNA. No relation with human herpesvirus-8 infection has been proven.
Histology: All angiosarcomas share the same pathological features. The tumor lobules are poorly circumscribed and have an infiltrative growth pattern. They contain large amounts of vascular tissue in a disorganized arrangement. The lining of the vascular spaces contains atypical-appearing endothelial cells. Mitoses are frequently encountered, as are intracytoplasmic lumina. The same tumor can contain well and poorly differentiated regions.
Treatment: The standard treatment is wide local excision with the goal of obtaining clear margins. This is usually followed by postoperative radiation therapy. The 5-year survival rate is low (15%-20%). Tumors that are metastatic or nonoperable can be treated palliatively with various chemotherapeutic regimens. The median survival time in these cases is 3 to 6 months.