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Why is my dog bruising and swollen after mast cell tumor biopsy?

Updated On September 23rd, 2025

Pet's info: Dog | Staffordshire Bull Terrier | Female | spayed | 41.8 lbs

Hi, my Staffordshire bull terrier has just been found to have a mast cell tumour on her hind leg. On Friday she underwent a biopsy and a fine needle aspiration of her lymph node to determine whether the cancer has spread. By Saturday afternoon her lymph node is quite swollen and she is rapidly bruising! I rang the vet and they said this is normal? Just wanting some peace of mind on the bruising as it has me greatly concerned. This picture is 36 hours after FNA.

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2 Answers

Most Helpful Answer

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Answered By Claudia Fioravanti

Veterinarian

Published on September 3rd, 2017

Hi, thank you for getting in touch with us. I totally understand your concerns, From the picture you are showing us, I would say that the bruising is excessive considering the small procedure. However mast cell tumours release substances that cause a lot of inflammation in the surrounding tissues, so this is what could have occurred to Sandy. I would recommend to have Sandy reassessed, if she is other ways well in herself, eating and drinking, tail wagging and comfortable you can make an appointment for tomorrow with your regular vets. If you are worried that she is unhappy, please take her in today. It would be best for you to see your own vet for continuity of care, because they have all Sandy's records and they did the procedure 36 hrs ago. Having said this, if you are not happy about the way your vets handle your concerns, I would go and see another vet. It would be interesting to know what medications is Sandy on. If you want to apply something just on the bruised area, Arnica is a natural but powerful ointment that helps a lot with bruising. I would not apply it where the dressing is. You just need to massage it gently so that it gets absorbed into the skin, 2-3 times a day. It is sold at the chemist under the name Arnicare cream. Also Lymph nodes in the area are quite deep, so I am thinking that maybe you are feeling something else ? Good luck, please get in touch if more advice is needed.

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    Answered By Dr. Massimo Orioles, DVM, Cert AVP, MRCVS

    Veterinarian

    Published on

    Yes that could be quite normal as mast cells can release certain substances (histamine) and create inflammatory reaction around the tissues where the tumor is. A major/systemic but rare allergic reaction can occur though in certain cases and if the bruising gets worse in the next hours I would strongly recommend a veterinary check up to rule it out. Please do not hesitate to contact us again on the forum or by requesting a consultation if you have any more questions or to discuss it any further.

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