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What is this painful pink lump on my 3-month-old puppy's armpit?

Updated On September 23rd, 2025

Pet's info: Dog | Mixed Breed Small (up to 22lb) | Male | 3 months and 2 days old | 2 lbs

My dog has a small pink lump under his armpit. He is 3 months old. I thought it may be a tick bite so I tried squeezing it some and he now crys when picked up if you touch the area on accident.

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4 Answers

Most Helpful Answer

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Answered By Ricardo Fernandez, DVM

Veterinarian, Veterinary Oncology Resident

Published on March 8th, 2018

Thanks for using Petco Pet Education Center, formerly Petcoach! This could be a benign or malignant growth. Given his young age, this could just be a small abscess or site of infection. This is often differentiated by a test called a fine needle aspirate (FNA) which is a pain free, inexpensive and easy procedure which in most cases will help reach a diagnosis. Sometimes a biopsy is needed for a definitive diagnosis. I recommend that you have him evaluated by your veterinarian for further assessment and treatment. I am really hoping for something benign. Good luck and have a good day!

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1Pet Parents found this answer helpful

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    Answered By Ricardo Fernandez, DVM

    Veterinarian, Veterinary Oncology Resident

    Published on December 3rd, 2017

    Thanks for using Petco Pet Education Center, formerly Petcoach! This could be a benign or malignant growth. This is often differentiated by a test called a fine needle aspirate (FNA) which is a pain free, inexpensive and easy procedure which in most cases will help reach a diagnosis. Sometimes a biopsy is needed for a definitive diagnosis. I recommend that you have him evaluated by your veterinarian for further assessment and treatment. I am really hoping for something benign. Good luck and have a good day!

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    1Pet Parents found this answer helpful

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    Answered By Ricardo Fernandez, DVM

    Veterinarian, Veterinary Oncology Resident

    Published on October 1st, 2017

    Thanks for using Petco Pet Education Center, formerly Petcoach! This is most likely a nodule or mass. This could be a benign or malignant growth. This is most of the time differentiated with a test called a fine needle aspirate which is easy, cheap and pain-free. Sometimes, a biopsy is required for a diagnosis. Have Jake evaluated by your veterinarian to have this test performed to try to sort out what the diagnosis is so that the best course of action can be determined. Keeping my fingers crossed that it is something benign!

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    2Pet Parents found this answer helpful

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    Answered By Angel Alvarado, LVT

    Licensed Veterinary Technician

    Published on November 2nd, 2017

    You can choose to either monitor it for rapid change/growth or make an appointment with Bailey's veterinarian to have the mass examined. A fine needle aspirate can be performed in the clinic to collect samples for pathology. This may lead to a diagnosis. See your vet sooner if the mass causes discomfort or restricts movement.

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