Fibrosarcoma in Cats


Fibrosarcoma in Cats


Photodynamic therapy for squamous cell carcinoma and other tumors

Question: Why doesn't Dr. Mike advise owners of cats diagnosed with squamous cell carcinoma about the new photo dynamic therapy being used?? My cat has a small lesion on the tip of his nose and was taken to Oklahoma State University, where they are carrying out a clinical study on PDT with great success. (Other facilities around the country are also using PDT with success, as are human medical facilities.) It bothers me to read so many questions from owners with cats that have similar lesions and know that they are not being advised of this ground-breaking therapy that could save their cats lives!

Answer: C-

Photodynamic therapy is a relative new procedure in veterinary medicine. It is considered to be promising for the treatment of superficial cancers, such as squamous cell carcinoma. Early studies of the response of cats with squamous cell carcinoma (SCC) to photodynamic therapy were only moderately successful (Peaston et. al., 1993) but more recent studies using newer photosensitizers seem to be more successful. This is an option for treatment of squamous cell carcinoma and other tumors, such as fibrosarcomas, that tend to occur on or near the skin surface.

Photodynamic therapy requires the use of specialized equipment and is not easily available in all areas of the country. It appears to be a viable option in areas in which it is available, though.

Mike Richards, DVM 9/14/2001


Question: Dear Dr. Mike,

I am a recent subscriber to the VetInfo digest. I hope you can help me with this question.

In January of this year my 7 year old cat "Moe" was diagnosed with a fibrosarcoma. The tumor was on the right side of his body wall. We are assuming that it is not vaccine related because he has never received shots in that location. My vet excised the tumor and reported that the margins were clean and that reoccurrence was highly unlikely. Two months later, however, another tumor had surfaced in about the same area. This time when the vet excised the tumor the cancer was 2 cm from the margin and he had me contact Tufts University veterinary school for an oncology consultation. The folks at Tufts were great and I feel confident of their skills and that they have my cat's best interests in mind. However, I am having a terrible time about making the decision to have the radiation/surgery/chemotherapy course of treatment prescribed to me by the doctors at Tufts. I have read other subscribers questions and your answers about the treatment and prognosis of this disease. I know animals react to these procedures differently than humans but I feel almost frightened from making a decision. The doctors have told me with the full course of treatments they give Moe a 50/50 chance of tumor control for two years. The treatments may include having some of his ribs removed. He's a very loving and outgoing cat now. I guess I am just concerned about his quality of life after going through all of this treatment and then to know that they only give him a 50/50 chance of living for two more years. It's a very frustrating and depressing situation.

I realize that this is a personal decision but I was wondering what your experience has been seeing cats who have gone through these treatments. Have you seen a cat survive longer than the two years after treatment? Have these cats been significantly impaired by the treatments?

I would appreciate any help that you can give me.

Thank you. Katherine

Answer: Katherine-

Removal of fibrosarcoma tumors has to be done very aggressively. It is often necessary to remove bone underlying the tumors, if it is possible to do that. Due to the highly invasive nature of this tumor, it may be better to ask the oncologist about having a good imaging of the tumor, using MRI or CT scans with a dye to help delineate the tumor. There are times when it is obvious that the tumor has spread beyond the realm of tissue that it is possible to reasonably remove. It may not be possible to get this type of scan done, or it may already be part of Tuft's standard policy to do something similar.

The first time we sent one of our patients off for this type of surgery we expected it to take months for the cat to feel better. We were very pleasantly surprised that she felt pretty good within a week to ten days of the surgery and that she did not quit eating during the recovery, at all. Our subsequent experiences have been very good, with only one exception. One cat did take several weeks to recover.

So far, we have one long term survivor from this type of surgery (four years at the present time). The other cats did well following surgery and I can not give you an exact accounting of the time they did well but I think it was more like a year to 1.5 years. Despite this, the owners who I have spoken with were still glad they made the choice to have surgery.

This is a very hard decision to make but I favor going ahead with surgery, personally.

Mike Richards, DVM 6/4/2000

Vaccine related Fibrosarcoma

Q: I am hoping you can give us some advice on how to proceed with some bad news we just received. Our cat has the vaccine related Sarcoma. She has a hard lump to one side of her spine. They took a biopsy of it (not through incision) and said it was cancer . This local vet is referring us to a surgeon and oncologist.

My questions are these:

1. Can surgery and treatment work? I mean, can she be cured. If it was your cat would you put it through surgery and possibly radiation? 2. We are located in Virgina also. Can you recommend the very best care? Are there specialists you know? 3. What will be the progression of this if we opt not to put her through the trama? How fast does it spread? Will she be in pain?

Thanks for your help. CP-

A: CP-

Surgery for vaccine related sarcomas works about 50% of the time. It works a lot better if a biopsy is done prior to the first surgery so that the surgeon knows that this is a fibrosarcoma from the outset. In that case, a surgeon who is familiar with surgery for aggressive cancers should be consulted and should perform the surgery. There is some chance that your vet feels comfortable with this but most general practitioners do not when the tumor is close enough to the spinal column to require removal of a portion of the spinal vertebrae. In your area there are several surgical specialists. I have taken my pets to Dr. Bradley, in Manassas, when they have required surgery I was not willing to perform and I have been happy with the results. Another very good choice would be NC State in Raleigh, NC. They have a good oncology staff. There is also supposed to be a new cancer specialty practice in Springfield. They seem to be interested in doing a good job but I have no personal experience with them. Your vet may have experiences with other practices in the area. The main thing is find someone who can plan the surgery properly and who is able to carry out the plan -- who will be able to remove enough tissue around the tumor to make total removal more likely.

Fibrosarcomas generally do not appear to be painful. They progress fairly slowly in most cases but it is best to remove them as soon as possible due to the difficulty in getting enough tissue around the margins as tumors grow in size.

The post surgical period can be painful but even with very aggressive surgery cats usually do surprisingly well. We have had three patients who had aggressive surgery for this condition and all three were doing very well within 6 weeks and two of them much faster than that.

Radiation therapy following removal of the tumor may be the best option. This is one reason to consult with an oncologist even if you use a surgical specialist for the actual surgery. Having both available in one place is an advantage of the veterinary schools and oncology specialty practices.

There are good pain relievers for the post-surgical time. It is possible to keep most cats reasonably comfortable. Talking about this with the surgeon prior to surgery is a good idea, too.

Hope this helps some. I am sorry for the delay in responding. I was out of town this weekend.

Mike Richards, DVM 9/9/99

Vaccine related Fibrosarcoma - continued

Q: Thank you so much for your response. But can you help clarify something? Should we take her to an oncologist first or right to a surgeon like Dr. Bradley? Our local vet set us up at the Springfield practice you mentioned in your e-mail - but with the oncologist not a surgeon. Do oncologists do surgery?

And with regard to the biopsy surgery (I am assuming that's surgery). Do they try to get the entire lump out at that time? Can you expand a little on this? Basically, is she going through 2 surgical procedures or one?

And how fast should this be completed? It's been about 4-5 weeks since the lump first appeared - -I sure of that timing. Are we acting too slow? I ask this because Dr. Bradley is booked up for a week but will do emergency surgeries of a vet calls to get her in. Is this one of those situations?

Thank you so much for your time. And believe me, $25 is not enough to give to this service (subscription). No matter what happens to Molly, we will make sure we spread the word and contribute more. This is highly needed. CP-

Thank you again

A: CP-

When a fibrosarcoma is suspected it is probably best to identify it first by biopsy of a small portion of the tumor (or even a needle biopsy using one of the needles that takes a core sample). If the tumor is a fibrosarcoma it is really important to do WIDE surgical excision. Wide enough that very few vets will do it on the presumption that a fibrosarcoma is present. There is good evidence to suggest that the initial surgical procedure has the best chance at getting all of the tumor so it is important to plan this surgery well. Due to this, I tend to think that seeing the oncologist first is best --- because they can tell the surgeon how much tissue has to be removed based on an evaluation of the biopsy results and knowledge of the cancer's location and the potential for post-surgical treatment. If the oncology center is not affiliated with a surgeon then another appointment has to be made. This can delay things some but if the planning is done properly, the delay is less important than proper surgical planning and tumor removal. There is always a strong desire to remove these tumors as fast as possible and it is best to get it done as fast as it can properly be done --- but again, doing it right is the most important thing.

Good luck with this.

Mike Richards, DVM 9/10/99

Fibrosarcoma on eyelid

Q: She is said to have a very low grade of firbrosarcoma over her eyelid. The radiation therapy I mentioned above is really the only thing to do. I have had several opinions and had 3 pathologists to look at the biopsy. they all say the same. In fact 2 of them which are not animal pathologists say that it bare resembles a fibrosarcoma. Should I do the radiation therapy where they do the seed implants and then keep my cat for a week in isolation or forget it. I want to do what is best for her. She is healthy but gets stressed out easily and I hate to leave her there for a week. The cost is not a problem, I just want the best for my baby. Please advise. thanks, Debbie

A: Debbie

It is not unusual at all for human pathologists to read veterinary samples much differently then a veterinary pathologist. There seem to be some big differences in tumor appearance and behavior among the animal species. I would definitely lean towards the veterinary pathologist's opinion about a cat tumor, although there are times when even veterinary pathologists disagree about tumors.

I have had mostly bad experiences with feline fibrosarcomas and therefore I tend to favor very aggressive treatment, such as wide surgical excision and then radiation therapy. If you have an oncologist you can work with you are already well beyond my expertise in finding specialized care. If the previous success rates reported by the oncologist seem reasonable to you then I see no reason not to attempt therapy. If there is little or no data then you'll have to trust the oncologist's opinion. This is one of those times when you might just have to go with your "gut feeling".

I hope things work out well.

Mike Richards, DVM


Q: Dear Dr. Mike: My Mother-In-Laws cat was diagnosed in June of 1996 with a fibrosarcoma mass on the spine. The cat was treated with surgery, the mass was removed and another mass was detected in June of 1997. The cat is currently being treated with radiation and will progress on to chemotherapy in the near future to deal with the current mass. No prognosis has been given and the vet has not said whether the mass has invaded the lungs or other vital organs. How can this be determined? Any help would be appreciated. Thank you, Debbie

A: Debbie- Unfortunately, it is probably reasonable just to presume that this cancer has metastasized to some other region of the body based on its reappearance. Fibrosarcomas are an extremely aggressive tumor and this would be the most common scenario. Chest X-rays are reasonably good at showing metastasis to the lungs. Metastasis to other organs can be very difficult to detect without going to something like MRI or CT imaging.

If you can speak with the oncologist handling your mother's cat's case, that would be best. They tend to know the latest in detection techniques, treatment options and prognosis.

Mike Richards, DVM


Q: Good Morning, My cat was diagnosed with Vaccine Related Fibrosarcoma about 3 months ago. About 3 weeks ago she had very radical surgery (her second) to remove a huge amount of skin on her back and she already has 2 lumps which have returned. My question is, is there any treatment, experimental or otherwise which can be used locally on these tumors to either get rid of them or inhibit their future growth? I decided against chemo or radiation because of the devastating effects on the animal and the cost was quite expensive. With both of those treatments, the percentage was still quite bad for survival/cure. I can't believe that there isn't something out there which can be used to treat these tumors locally. Please help me if you can, I am grasping at anything in an effort to save my pet. Had I been given all of the information relating to vaccinations, I would have made a different decision and would not be going through this right now. Please help me if you can. Best regards, Kim

A: Kim- To the best of my knowledge there is no medication which can be applied topically that will treat (reduce in size or "kill") a fibrosarcoma. I am pretty sure that if such a product is found it will be heavily advertised. There are current research efforts aimed at determining if chemotherapeutic agents can be injected directly into surface tumors to reduce the side effects and still effect a cure. There is also current research in other areas of tumor control such as genetics that may be beneficial but which may take years to come to fruition.

I wish that I could help you more with this. It is a very frustrating problem in veterinary medicine right now and everyone would like to know more about the risks, causes and treatment of these tumors. Mike Richards, DVM


Q: My brother-in-law has the most charming aby cat about one year old now. They found a small mass in the nape of the neck where they give inoculations and removed the mass. They were told that the mass was the result of a rare reaction to the kitten shots and occurs very rarely in cats. They were also told that the cat may not live beyond a year if the mass grows back. Do you know of this rare problem associated with the kitten shots.

What other options do they have? Many thanks, Geri

A: Geri- The current estimate is that about 1 in 3000 cats will develop fibrosarcoma and that the fibrosarcoma is likely to occur at a vaccination site. This probably occurs because of reaction to the adjuvents in the vaccine -- irritating compounds included to increase its effectiveness. Fibrosarcomas are very aggressive tumors and a wide surgical margin -- at least an inch in EVERY direction is necessary when removing these to try to prevent spread of the tumor. Since an inch below these tumors often includes the bones of the spine there is a strong tendency among veterinarians not to be this aggressive. When it is likely that surgery did not include sufficient tissue around the tumor it may be helpful to consider radiation therapy if that is possible. If your vets feel confident that they removed a very wide margin there may be little benefit to additional therapy. I am not absolutely certain of this statistic but I think about 50% of the time surgical removal prevents recurrence of the tumor. When surgery doesn't work to stop the spread of this tumor the prognosis is poor for long term survival.

If histopathologic exam of the tumor was not done, there is a reasonable chance that it is not a fibrosarcoma which would increase the odds of a successful outcome.

I hope that your brother-in-law's cat does OK.

Mike Richards, DVM


Q: Dr. Mike, My sister called me and is extremely distraught because her cat has been diagnosed with a form of cancer called "fibro sarcomo." Kitty had a tumor removed from her leg at the end of last week and my sister has to decide in the next day or two if she should or should not amputate the leg. She does not want to go through with the amputation if it will only add a month or two to the cat's life. On the other hand, if the cancer is localized, then the cat could live for another 7 or so years (she's only 8 years old). The vet told her the cells were "undifferentiated" and that it was a rapidly growing tumor that was removed. Do you know where she can find out more information about this type of cancer and what the cat's chances are of surviving after an amputation? M.

A: Fibrosarcomas are highly malignant (spread quickly) tumors. They can occur for no apparent reason and they also occur in some cases as a form of vaccine reaction at vaccination sites. Obviously, this is a serious side effect when vaccinations are implicated as the cause.

I was at a seminar on oncology last year and if I remember correctly, the speaker said that amputation will work to prevent metastasis (spread) of this tumor in about 50% of the cases. Presumably it has already spread in the cats in which this doesn't work. It is recommended that the amputation be followed up with radiation and/or chemotherapy if possible.

Fibrosarcomas on any part of the body in which they can be surgically removed and then treated with radiation therapy and chemotherapy have about a 30% survival rate after 18 months or so, as reported by oncologists on the Veterinary Information Network. I am assuming that it is possible to get a much wider surgical margin when amputating a leg and that the difference in survival times relates to that. It is very hard to get an inch or two of clean margin around one of these tumors in any other manner --- that inch has to be in ALL directions and if the tumor is on the body, it usually means removing the body wall below the tumor, a difficult task in many cases.

As odd as this may sound, I do not know what the survival time without treatment is, nor did I find any study referring to one. From experience, it seems much shorter than 18 months, though.

Amputation is always a difficult choice to make. Most cats do very well on three legs, though. I do not recall a client who was upset at having made a decision to amputate in order to try to prolong a pet's life in our practice after the fact. It is just surprising how well pets do after amputation.

Mike Richards, DVM

Vaccine Related Fibrosarcoma in Cats

Q: DDear Dr. Mike: I have a 5 yr old healthy tabby, and I have noticed a lump on his right side near his spine right near his hip bone. The lump does not seem to bother him. He is carrying on as usual. It is in the location where he has always been given his vaccines. He has always been healthy until now. I have taken him to my veterinarian and she did a cytology in house. She said the cells taken show evidence of Fibrosarcoma. She said this is something recent in the past 10 years where there have been vaccine induced tumors. I find this very odd, that a distemper shot, (which is required) could result in possible complications 6 months later. Now I am faced with having to pay hundreds of dollars to have the tumor removed and a biopsy. Let me also mention that this is something that will continue to return, as I am told, and will probably shorten his life. I need a second opinion. Thank you.

A: Unfortunately, cats do develop vaccine related fibrosarcomas. This is a problem which has come to light in the last few years and it is one for which there is no clear consensus about the proper way to publicize and deal with it among small animal veterinarians.

To the best of my knowledge, no one knows the exact rate of occurrence of these fibrosarcomas as a result of vaccination. This is a tumor which can occur naturally, without the influence of vaccination, making it even harder to pin down any sort of specific numbers. At present, it is generally believed that these can occur as the result of any of the vaccines normally used in cats.

It is hoped that vaccines produced with recombinant gene technology may eliminate this reaction as they are possible to make without adjuvents, the irritating substances included in vaccinations in order to make the body react to them. It is also very likely that the nasally administered vaccinations will be less likely to cause this problem. These vaccines have been unpopular because they sometimes induce mild to moderate symptoms of the diseases they are meant to protect against. People didn't like that but it may be better to have a regular risk of sneezing rather than a less common, but extremely serious risk of cancer.

It is very important to do a thorough job of removing the tumor and all tissue surrounding it for at least 2 to 3cm in all directions, including underneath the tumor. This is a major surgery. There is some evidence that radiation therapy after surgical removal of the tumor may help prevent recurrence, if that is an available option. Despite very aggressive efforts to remove all of the tumor it is likely that 50% or so of these tumors will recur anyway. The first surgery is by far the best chance at getting it all, so it is necessary to do it right.

I am sorry that you were unaware of this risk. I suspect that most cat owners are. Most veterinarians are reluctant to tell every cat owner about the risk of fibrosarcomas and to explain the risk/benefit ratio of vaccination for each individual cat. I believe that would be the best approach to take and do discuss risk vs. benefit of vaccinations with many of my clients but not nearly all of them. It is not a good idea to abandon vaccination entirely since the disease we are attempting to protect against can be an even bigger risk to the cat but it is important to assess the risk/benefit ratio and to vaccinate only when necessary.

Without any sort of quantification of the risk of the tumors post-vaccination, I think that many vets are just sort of feeling their way through this situation and hoping that sometime soon there will be some sort of clarity. Veterinarians have always viewed vaccines as pretty benign and often had the attitude that the risk of vaccination was so small that there couldn't be a smaller risk of getting the disease. Now that we know that vaccines are not always benign, we are undergoing a painful shift in thinking -- and it is painful and difficult for many of our patients and clients as well.

While all of this might help you understand the background, the bottom line is that aggressive surgical excision is the best hope for successful treatment and that even more aggressive therapy with radiation could be called for. The prognosis is as you described it and the situation really is depressing and even maddening.

Mike Richards, DVM

Last edited 01/30/05


Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...