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My dog has a bump. Can vets diagnose mast cell tumors by microscope?

Updated On September 23rd, 2025

Pet's info: Dog | Mixed Breed | Female | spayed | 9 years and 2 months old | 4 lbs

Would a Vet have been able to diagnose a mast cell tumor on a microscope? I don’t want it to be that. Precious got blood tested from a bump & the doctor said she nor anyone else there trained to know what kind it is. She said it was all of the same cell though & I think she said they were tightly packed. She’s having it removed but I’m scared it’s something bad. It has never bothered her. It’s been there since June & has only grown a tiny amount but it’s still small. It got softer afterwards

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4 Answers

Most Helpful Answer

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Answered By Laura Johnson VMD

Veterinarian

Published on April 7th, 2018

Hi, thanks for using Petco Pet Education Center, formerly Petcoach! It depends on the Vet's experience with reading cytology. Most Vets send out their cytology samples to a specialist who is trained to read them. Mast cell tumors have a classic look and tend to be one of the easier tumors to diagnose. You could ask your Vet to send the slides out since that only takes 1-2 days to get them back but sometimes aspirates do not get you an answer. I know you have surgery set up and a biopsy planned. That is the best thing for Precious, to get the mass off and know what it is. It has a high chance of being benign. It is a good thing it hasn't grown much. I wish you the best!

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    Answered By Makenzie Kurth, DVM

    Veterinarian

    Published on April 7th, 2018

    Many veterinarians can identify mast cell tumors under the microscope. However, sometimes they can look different than expected so we can’t say for sure. But if it had all the same cells, it should go. It looks small and your vet should be able to take plenty of surrounding tissue in that area so hopefully that will be the end of it. You can always have that tissue sent to the lab to have it identified for sure. Best of luck to you and Precious!

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    Answered By Ana M, DVM

    Veterinarian

    Published on April 7th, 2018

    Thank you for submitting your question regarding Precious. A fine needle aspirate is an in office procedure used to diagnose a skin mass. The cells are collected and evaluated under the microscope. A mast cell tumor has distinctive cells and many times can be identified in this way. If the cells are questionable, the slides can be submitted for a review by a pathologist. Alternatively, the mass can be surgically removed and the whole mass submitted to the laboratory for diagnosis. I hope this information helps!

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    Answered By Rebecca, DVM

    Veterinarian

    Published on April 7th, 2018

    Thank you for using Petco Pet Education Center, formerly Petcoach. In many situations surgical removal and histopathology by a trained pathologist is the only way to get a definitive diagnosis. Fine needle aspirate (sticking a needle in mass to get cells) may give an impression of they type of mass, but it is not a firm diagnosis. Many times removal can be curative as well as diagnostic. Best of luck for a good diagnosis and outcome for Precious.

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