Spindle Cell Sarcomas

Spindle cell sarcomas are cancerous tumors that affect the connective tissue and soft tissue of the dog and cat. A tumor is classified as "spindle cell" when it is impossible to distinguish exactly what type of neoplasia is taking place, either due to unusual behavior or growth patterns. Malignancy can often be predicted by the tumor's rate of growth, and though any cancer diagnosis is frightening, most spindle cell sarcoma cases can be treated.

Identification

• Spindle cell sarcomas can come from fat-producing cells, nerve cells or smooth muscle cells. In fact, this very characteristic of these tumors is what makes them difficult to classify. According to the Merck Veterinary Handbook, it is thought that the origin of all spindle cell tumors is a mesenchymal cell that can develop into a number of different things. This is why even though the tumor may share characteristics with a certain type of cell, it doesn't mean that it came from that cell. Spindle cell sarcomas can occur superficially or deep in the body, and can be benign or malignant. Even this is a difficult distinction because in most cases, the tumor spreads locally but is not considered malignant. It is also not considered benign because benign tumors do not spread. Each case of spindle cell sarcoma is different, and should be treated accordingly.

Diagnosis

• A pet with spindle cell sarcoma will usually present with a lump just underneath the skin. The lump may have been growing slowly over time, or it may have sprung up seemingly overnight. Most are solid, but some can contain a small amount of fluid. A small-needle aspirate may not produce a sample large enough for diagnosis, but a biopsy can be performed quickly and with only local anesthesia. The veterinarian will examine the tumor cells microscopically to see what type of cells are present, and will take the patient's history into account. A tumor that is small and has grown slowly is likely to be benign, while a large tumor that has grown quickly is likely to be malignant, especially if it is located deep under the skin. X-rays can reveal whether or not the tumor has spread.

Surgery

• Surgery to remove the tumor is the treatment of choice. If the entire tumor can be excised with a wide margin of normal tissue surrounding the site, the chance for recovery is good. Occasionally, removal of the entire tumor is impossible, or the tumor may have already spread. In these cases, the vet will remove what she can, and will follow up with additional therapy to halt the growth of the remaining neoplastic cells.

Treatment

• After the dog has healed from surgery, radiation treatment can begin. According to DVM 360, a typical plan of 15 to 20 treatments given over three to six weeks can result in control of the neoplasia at a rate of 50 to 90 percent at three to five years. Many of these tumors do not respond to chemotherapy, but for dogs with inoperable, malignant or very large tumors, it may be helpful as palliative care.

Prognosis

• As long as the tumor can be removed and kept from spreading, the prognosis is good. If the tumor was partially excised, the remaining neoplastic tissue can cause it to reoccur. If the tumor was not removed, or if it was found to be high grade after removal, the prognosis is guarded. Results can still be obtained for these patients with radiation and chemotherapy.