Resource Library: Sarcoma

SOFT TISSUE SARCOMA
Soft tissue sarcomas are tumors that arise from mesenchymal cells. These are cells that make up the supportive structures of the body such as muscle, fat, connective tissue, and those cells that line vessels and nerves. As these tumors are named after the structures from which they arise, some examples of soft tissue sarcomas are; fibrosarcoma, myxosarcoma, leiomyosarcoma, rhabdomyosarcoma, neurofibrosarcoma/hemangipericytoma/nerve sheath tumor/schwannoma, liposarcoma.

They are considered to be locally invasive (i.e. cause problems due to invasion or compression of the surrounding tissues where they arise) although recent evidence would suggest that they have the ability to metastasize also. The potential for metastasis is grade dependent. There are three grades of soft tissue sarcomas, 1 to 3 (also called low, intermediate and high), where grade 1 is the least aggressive and grade 3 the most aggressive.

When these metastasize, they go to the regional lymph nodes and lungs. The predictor of survival time has been found to be the grade of the tumor. Whether the tumor will recur is dependent on the ability to remove it in its entirety. This is called the margin. If the margins are complete (or clear of tumor cells), recurrence is less likely. With a surgery site that has tumor remaining in the area, recurrence is more likely. The rate has historically been reported to be 25-62%. One study found recurrence in 15% of cases, metastasis in 17% and death from disease in 33% of cases when a series of 75 dogs with soft tissue sarcomas were evaluated. This study also found the median survival time to be 1416 days.

The treatment of choice for soft tissue sarcomas is complete surgical excision followed by chemotherapy or radiation if the tumor is high grade. Prognostic factors for soft tissue sarcomas are; small size, superficial tumors, low grade and movable masses (i.e. tumors that are not fixed to underlying tissues). Some large tumors that are not resectable can respond to radiation therapy.

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