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Dr. Loretta
Dr. Loretta, Cat Veterinarian
Category: Cat Veterinary
Satisfied Customers: 28121
Experience:  25 years of experience treating cats in my practice.
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I found a very hard lump on my cats left hip a few days ago

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I found a very hard lump on my cat's left hip a few days ago (about 1 cm long and .5 cm wide). She had rabies done about 2 months ago (but I read that rabies are done on the right side). She is acting normal - eating, jumping, etc. she is 5 years old. I took her to the vet and after doing needles aspirate, the following report came back from cytology. How does this sound to you? how often on average do cytology reports disagree with excisional biopsy results? Are tumors in cats more often benign or malignant?
Thank you!
CLINICAL INFORMATION
Mass at the site where vaccine injection likely given in past
SOURCE
Hard small dermal mass on right rear left leg/thigh
DESCRIPTION/MICROSCOPIC FINDINGS/COMMENTS:
DESCRIPTION:
The slides contain a small amount of peripheral blood as well as a moderate number of mesenchymal cells. These cells have oval to elliptical nuclei with prominent nucleoli. Cytoplasm is variable with some circumferential and some polar. The cells are present singly and in variably sized clusters. No infectous agents are seen. There is no evidence of inflammation.
MICROSCOPIC FINDINGS: MESENCHYMAL PROLIFERATION
COMMENTS:
The cytomorphology of the spindloid cells appears relatively benign, however because location and probable association with prior vaccines there is increased concern for possible vaccine associated sarcoma. Granulation tissue formation, fibrosis/fibroplasias, and spindle cell tumors may all appear similar cytologically and should be included in the list of differentials. Biopsy or complete surgical excision with histopathologic evaluation is recommended for a definitive diagnosis and accurate prognosis.
Hi there.

This description of the cells from the biopsy are indicative of a benign mass but since they cannot be actually determined, the pathologist tells us that there is a possibility that this mass could be the beginnings of a vaccine induced fibrosarcoma. If this is the problem, this is extremely serious for your cat and removal with a wide excision is the best course of action at this point in time.

Have your vet remove this as best they can and then they will monitor this closely for months.

http://www.petplace.com/cats/injection-site-sarcoma/page1.aspx

Click CLOSE WINDOWS to get into this site.

Good Luck!!


Customer: replied 6 years ago.

thanks so much for your reply.

Can you please tell me - based on your experience, how often on average do cytology reports disagree with excisional biopsy results? Are tumors in cats more often benign or malignant?

Most often, if this is a Fibrosarcoma which is not a malignant cancer, the pathologist can usually determine this on the first biopsy. I would be surprised if the second biopsy revealed a Fibrosarcoma but it is possible. These tumors even though they are not malignant can become deeply rooted and almost impossible to remove entirely.

Most tumors such as this in cats are benign, luckily.
Customer: replied 6 years ago.

Fibrosarcoma is not a malignant cancer?? what do you mean?

This is a cancer that does not spread like other tumors throughout the body which is the meaning of malignant but, as I said before, it is extremely invasive.


http://www.marvistavet.com/html/body_vaccine_associated_fibrosarcom.html
Customer: replied 6 years ago.

thanks so much for your time and for the articles - I really appreciate it.

Just one last thing.....since fibrosarcoma is not a malignant cancer, wouldn't the cells be appearing benign cytologically? I am sorry to keep bugging you......

Customer: replied 6 years ago.

one more thing - I am really sorry......

I just remembered one important fact. Banfield hospital, where my cat got her rabies vaccination 2.5 months ago, says that they always do rabies in the right side (the lump is appearing on my cat's left side). However, when my cat was getting her rabies injection, the doctor accidentally dropped the medicine from the syringe (she thought she injected it into the cat, but apparently injected it onto the table. So, she went to get a new syringe so that she could do it again. But I don't remember where she injected it after. And Banfield has no notes about the incident. Am just wondering, if you were in that situation, which side would you inject for the 2nd time (if you dropped the medicine the first time) - would you try the right again or would you do it to the left? Weird question, I know....but am trying to figure out whether it is the place of injection or not.....

This is not a weird question at all. We always give the rabies vaccine in the right hip for this reason...so we know if anything is associated with the injection. This vet would have put the other injection in the right hip...or at least I would.

This is actually a good sign...
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