Why does my dog have a new mammary lump and swelling post-surgery?
Updated On September 23rd, 2025
Pet's info: Dog | Shih Tzu | Female | spayed | 10 years and 8 months old | 12 lbs
My 10 year old dog had a lump in her 4th left mammary gland, so we had it removed. The test came back inconclusive, so we don't know if it was malignant or not. Her vet recommended having her sprayed as well, so she had two procedures done. It has been a month since her surgery and now there appears to be a quarter size lump near her 4th right mammary gland. Also, near her vulva, where her stitiches were, looks a little swollen.
5 Answers
Most Helpful Answer
Published on October 30th, 2017
I would be concerned that the swelling is another mammary mass or lymph node from the mammary area. Unfortunately, needle aspirates on mammary cells can be hard to determine if malignant or not. I would recommend taking Aries in to your vet tomorrow to discuss the next steps. I think your vet will also suggest chest xrays to make sure there is no evidence of cancer in her lungs.
1Pet Parents found this answer helpful
Related Answers from Veterinarians
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Published on
Thanks for using Petco Pet Education Center, formerly Petcoach! Mammary tumors in dogs are malignant in about 50% of cases which makes it possible that her previously removed tumor was malignant in nature. I recommend that you check with your veterinarian for further staging (to check for any evidence of metastasis or spreading) which should include thoracic radiographs and abdominal ultrasound as well as sampling of this lesion. If no evidence of metastasis is noted and it does appear to be a tumor, a lumpectomy is recommended. If confirmed an adenocarcinoma, chemotherapy is generally recommended. Feel free to request a consultation with me if you would like to obtain further information as this is a type of issue I deal with very commonly and could give you more information after gathering more information from you about her case. Good luck and have a good night!
1Pet Parents found this answer helpful
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Published on June 13th, 2017
Poor Hooch! I understand your concerns. Her tumor is quite pronounced and is suspicious for a mammary gland tumor given the location. Fortunately for dogs, 50% of these tumors are benign. However, it is concerning that it has gotten this large over a few months. Hooch should go to the vet sooner rather than later and will likely need to have this mass surgically removed and biopsied to determine if it is benign or malignant. Your vet will also discuss if chest x-rays are indicated to determine if cancer has spread to the lungs (if this mass is malignant). I hope that all goes well!
1Pet Parents found this answer helpful
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Published on April 1st, 2019
Hi there and thank you for using Petco Pet Education Center, formerly Petcoach to address our concern. Judging from the photos, it appears that the mass is associated with the mammary gland. Some dogs can have a larger amount of fat and glandular tissue that is normal and nothing to be concerned about. However, this could be a primary mammary mass that needs further testing. I would recommend having a veterinarian take a look at this so that the most appropriate diagnostic and treatment recommendations can be made. I hope this helps guide you in the right direction. Please let me know if you have any other questions or concerns and I would be more than happy to help you further.
1Pet Parents found this answer helpful
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Published on November 5th, 2016
As she is unspayed, high chances it is mammary gland cancer, with all the surrounding symptoms there is unfortunately a good chance that the cancer has already spread. You should take her to the vet ASAP in order to have a blood test done as well as an xray to confirm this suspicion.
1Pet Parents found this answer helpful
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