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Feline Fibrosarcoma

Fibrosarcomas in cats are fairly commonly observed veterinary medicine and occur in humans as well.  As with many kinds of cancer, the reasons a fibrosarcoma develops, and the location where it develops, may be at best speculative.  We really do not have all the answers yet.  On occasion in veterinary medicine we observe vaccine induced cancer called fibrosarcoma.

A FIBROSARCOMA is a malignant (invasive) cancer originating from fibrous connective tissue.  Fibrosarcomas may spread (metastasize) to other areas of the body.

A FIBROMA is a benign (non-invasive) neoplasm (tumor) composed primarily of fibrous tissue.  These do not spread to other areas of the body.

In recent years the topic of vaccine induced fibrosarcomas in cats has been a serious concern of cat caretakers, veterinarians, and the pharmaceutical companies that make vaccines for cats.  Unquestionably, vaccinations have prevented uncountable deaths in dogs and cats through the years.  Just as in human medicine where such diseases as smallpox and polio are no longer health threats due to wide distribution and use of vaccines, so too in veterinary medicine have serious diseases been kept in check by intelligent use of animal vaccines.  

However, there can be a downside to the wonderful miracle of vaccines.  On occasion, and that occasion may be only a single adverse reaction in 50,000, there may be an undesirable outcome for the patient receiving the vaccination.  Read Dr. Dunn's article on the use of vaccines in dogs and cats.

One unique type of adverse reaction is seen in cats after having been vaccinated for certain feline diseases.  Adjuvants are often added to killed (inactivated) vaccines to enhance the immune response; a common adjuvant is aluminum salts and these aluminum deposits are often seen in the microscopic analysis (histopathology) of a section of the offending tumor.  There is speculation that adjuvants may be the inciting agents that stimulate a reaction at the vaccine site and which eventually leads to cancer formation.  All the facts are not known at this time and many researchers are currently working to find the answers to the vaccine induced sarcoma problem in cats.
  
Progress is being made, though, and scientists and veterinarians are beginning to understand the complex variables that factor into tumor formation at vaccine sites.  Some of those factors are location of vaccine administration, type of vaccine and adjuvant, frequency of vaccine deposition in a localized area of the cat, and the state of health of the cat at the time of the vaccination.  Hopefully, in the near future these variables will be understood and adverse vaccine reactions will no longer be a consideration when we attempt to protect our feline friends from some very real and dangerous diseases. 

Fibrosarcoma Removal In A Cat
[Click on an image to see a full size version]

This patient, a 16 year old domestic long-haired cat, was presented with a rapidly growing mass over the back near the shoulder blades.  The physical exam was otherwise normal and the blood chemistry and blood cell analysis of the patient was normal.  Surgery was elected as a method of prolonging the patient's life.  The patient was anesthetized with Isoflurane inhalant anesthetic and recovered quickly and with no complications.
The site over the shoulder  blades is prepared for surgery	The surgeon begins the incision	The mass is carefully isolated.   This mass had a large  cyst within it
Any observable abnormal tissue  is removed... difficult when  there is tumor invasion of  surrounding healthy tissue.	The tumor bed is carefully  inspected for abnormal tissue	A view of the excised tumor
A view of the depth of the tumor	Vaccinations are a very important  health care tool.  Consult with your veterinarian for recommended protocols.	The surgical area immediately  post operatively. Sutures are  removed 10 to 12 days later

The histopathology report on two areas of the excised tumor follows:

DIAGNOSIS:  Haired skin, subcutis and skeletal muscle from back: FIBROSARCOMA.
COMMENT:  Within the subcutis and skeletal muscle there is a malignant neoplasm composed of mitotically active spindle cells that have produced collagen.  Completeness of excision cannot be judged.  Neoplasms of this type are locally invasive and prone to local recurrence; eventual metastasis occurs in some cases.

In this patient, frequent monitoring of the surgical site will be needed in order to reveal any new tumor growths at an early stage.  Removal of small nodules of tumor are much less invasive for the patient and usually will provide for more thorough removal than tumors that have had the chance to grow over long periods of time.

Update:  This patient was euthanized one year after this surgery.  The tumor regrew and the pet owner elected not to have any additional surgery performed.  The owner was happy that an additional year of reasonably happy life was enabled by the first surgical procedure.

Related pages for your information:
Back to the main Surgery Room
Do you vaccinate your own pets? Read this before you do.
Read Dr. Dunn's article on the use of vaccines in dogs and cats.

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