Soft Tissue Sarcomas

Soft tissue sarcomas tend to occur in older adult animals. These tumors involve mesenchymal cells, such as fibroblasts or the Schwann cells of nerve sheaths. The three most common types of sarcomas in dogs are:

• Fibrosarcomas;
• Nerve sheath tumors;
• Hemangiopericytoma, which include spindle cell sarcomas or dermatofibrosarcomas.

Fibrosarcomas are most commonly observed in the dog's midsection, the mammary glands, and on the limbs or face. Nerve sheath tumors usually involve spinal or cranial nerve roots, and occur most commonly on the midsection and limbs. Hemangiopericytomas are thought to arise from specialized cells (pericytes) that surround small blood vessels, and these may also involve nerves. They most commonly occur in the limbs. Dog breeds predisposed to sarcomas are boxers, German shepherds, and cocker spaniels. While soft tissue sarcomas are less likely to metastasize to other parts of the body, the tumor often aggressively invades local tissues, and may recur in the same or different location even following excision by the surgeon.

The methods used to diagnose soft tissue sarcomas are an initial cytological examination and radiographs, followed by a biopsy and histopathological examination for definitive diagnosis. Biopsies taken from the margins of the tumor are recommended, in order to determine the likelihood for tumor recurrence.

Treatment of Soft Tissue Sarcomas

The treatment for soft tissue sarcoma always includes surgical excision, performed at the earliest stage possible. Wide excisional margins are required because these tumors tend to be locally invasive. If the surgeon cannot completely excise the tumor, radiation may be used to kill remaining c ells. These tumors are often resistant to low doses of radiation, so high dose radiation therapy is usually required for control of the disease. Chemotherapy is generally not used because these tumors infrequently metastasize to other parts of the body, although this can occur. The combination of surgery and radiation is often successful, unless the tumor has already metastasized or recurs.

Antiangiogenic treatments may be useful in controlling soft tissue sarcomas. Fibrosarcomas are known to depend upon new blood vessels for growth. Inhibiting angiogenesis in animals with fibrosarcomas has slowed the disease, or in some cases, achieved regression. In human patients, the antiangiogenic drugs Vitaxin and endostatin have been reported to shrink sarcomas in individual cases. The Angiogenesis Foundation has successfully treated a canine with recurrent fibrosarcoma using antiangiogenic therapy (OLCAT-007), and is now studying this strategy more widely in other dogs.