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Key takeaways


Soft tissue sarcomas are a group of tumors that arise from the connective tissue, muscle, or nervous tissues in cats. 

  • This group of tumors includes fibrosarcoma, leiomyosarcoma, peripheral nerve sheath tumors, myxosarcoma, and injection site sarcoma
  • Soft tissue sarcomas often invade surrounding tissues and are typically on the trunk, mammary glands, limbs, and head, but can also develop in the abdomen
  • Symptoms depend on tumor site and extent of invasion and include visible lumps, limping, vomiting, weight loss, and diarrhea
  • Potential causes include feline sarcoma virus, foreign bodies, and injury
  • Diagnosis involves diagnostic imaging  and tissue biopsy
  • Complete surgical removal is best to maximize outcomes, but is not always achievable
  • Other treatments include radiation and chemotherapy
  • Prognosis ranges from good to guarded depending on the tumor and treatment
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A closer look: Soft Tissue Sarcomas in Cats


Soft tissue sarcomas are the result of uncontrolled cell growth in the soft tissues of the body. This can include muscles, nervous tissues, and connective tissues. They are notorious for being locally invasive but are not as likely to spread as other cancers. Soft tissue sarcomas are sometimes compared to an octopus, with the bulk of the tumor representing the head, and the microscopic invasive cells representing the tentacles.

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Risk factors


Soft tissue sarcomas are common, especially in older cats, and are serious and can be life-threatening. Anytime there are lumps present, veterinary care is warranted. Regular veterinary visits may help to catch symptoms early and improve the outcome.

Possible causes


Soft tissue sarcomas arise from abnormal, uncontrolled growth of certain types of cells in the skin and subcutaneous connective tissues, including muscles, small blood vessels, and nerves. There is no single cause. Feline injection site sarcomas are associated with certain types of vaccines. Some soft tissue sarcomas are caused by a form of the feline leukemia virus called feline sarcoma virus. Any of these tumors can also be associated with radiation therapy, trauma, or foreign bodies (i.e., orthopedic implants).

Main symptoms


Symptoms of soft tissue sarcomas are related to the tumor site and invasiveness of the tumor.

Testing and diagnosis


Diagnosis of a possible soft tissue sarcoma begins with a complete physical exam, blood work, and urinalysis. X-rays of the chest may be indicated to rule-out metastasis. CT, MRI, and ultrasound may also be utilized to fully characterize the tumor. Sampling of the tumor is essential for a definitive diagnosis, grading of the tumor, and guidance for treatment. Any enlarged lymph nodes may be biopsied as well.

Steps to Recovery


If the tumor has not spread, surgical removal of the tumor is the treatment of choice. If the tumor has a clear outline, surgical excision can achieve a cure in 90% of patients. Often tumors recur if excision has been incomplete, and recurrent tumors tend to be more malignant. Injection site sarcomas in particular require very large surgical margins and have a high rate of recurrence (>90%). Radiation therapy may be initiated as an adjunct treatment in these cases. Chemotherapy in combination with surgery and/or radiation may also be useful if spread is present, and to reduce symptoms.

Prognosis depends on the grade of the tumor and the treatment chosen. The tumor grade is predictive of outcome and recurrence. In general, smaller, more superficial and slower-growing tumors are less malignant than larger, faster-growing tumors in deeper tissues. In cases of higher-grade, recurrent tumors, humane euthanasia may be considered.

Prevention


As there is no single cause of soft tissue sarcomas, there is no clearly identified prevention. Soft tissue sarcomas are not contagious to humans, but feline sarcoma virus is contagious between cats. Appropriate vaccination and keeping cats indoors may prevent the feline sarcoma virus. The use of non-adjuvanted vaccines and avoidance of polyvalent vaccines can reduce the risk of injection site sarcomas. Vaccinations may be given in the limbs or tail to facilitate amputation if necessary.

Are Soft Tissue Sarcomas in Cats common?


Soft tissue sarcomas are common in cats. Fibrosarcomas are the most common type of soft tissue sarcoma in cats.

Typical Treatment


  • Surgical excision
  • Radiation
  • Chemotherapy
  • Symptomatic relief (palliation)
  • Humane euthanasia

References


SKIN STS
No Author - Writing for Veterinary Society of Surgical Oncology
Soft Tissue Sarcomas
Malcolm Weir, Christopher Pinard - Writing for VCA Animal Hospitals
Connective Tissue Tumors in Animals
Alice E. Villalobos , - Writing for Merck Veterinary Manual
SOFT TISSUE SARCOMAS IN CATS
No Author - Writing for PetCure Oncology

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