My dog's vet suspects a mast cell tumor. How serious is this?

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!

Hello and welcome to Petco Pet Education Center, formerly Petcoach. I am sorry that Max has a lump. FNA (Fine needle aspirate) is the name of the procedure your vet performed. Some types of cancers, including Mast Cell Tumors, will exfoliate (give off) a lot of cells when this procedure is performed, and have a very classic appearance under the microscope. Therefore yes, this is a proper procedure and diagnostic test. I would recommend that you chat with your vet about staging (looking to see if the cancer has spread to other locations of the body- usually using ultrasound and chest x-rays), and if it has not, have the tumor removed. Ensure you chat with your vet about if they are comfortable doing the surgery to get proper margins (3cm diameter and 3 facial planes) or if a surgical specialist is required. This will depend on the location of the mass. Best of luck with Max, hopefully it is a low grade and will be cured with surgery!

I’m sorry to hear about Tsunami’s diagnosis. MCTs are quite common in dogs, and unfortunately due to the cell distribution around the primary tumor, incomplete margins are common. If you want to be confident you’re pursuing the best options for the best prognosis, I recommend asking your vet for an oncologist referral. A veterinary oncologist will be the best specialist to be able to present all the options and their given pros & cons, and they have access to chemo medications that most primary vets don’t carry. If you choose not to pursue referral, then I recommend reaching out to your vet again to discuss the next step. If this were my case, I would probably recommend sampling Tsunami’s lymph nodes with a needle to look for evidence of regional metastasis, and based on those findings discuss if a second surgery is appropriate. Hope this helps!

It's difficult to recognize mast cells as abnormal on cytologic evaluation. Usually, when a mast cell tumor has metastasized to the spleen, there is a nodule in the spleen that can be visualized with ultrasound or at surgery. Just taking a random aspirate of the spleen and finding normal mast cells does not necessarily prove metastasis, but a recheck ultrasound in 3 months should be helpful if you are still concerned.

Hello, and thanks for using Petco Pet Education Center, formerly Petcoach. A needle aspirate is the standard way to get an initial "suspected" diagnosis on a lump, but there are limitations to what a needle sample can tell us. If the cells in the needle sample appear worrisome, then the next diagnostic step is to send in a biopsy (surgical "chunk") of the tumor, or to remove the tumor itself and send the whole thing in to the lab for analysis. So, was removal of the ear necessary? I can't say, I don't know enough about the location or size of the mass. I didn't see the slide from the initial needle aspirate. But if the needle aspirate looked worrisome, and the next step is to remove the tumor or cut a piece of the tumor off, then removing that piece of the ear may have been the only way to find out for sure what the tumor was, and whether surgical removal was curative. Rather than regretting in hindsight that the surgery was done because the histopathology report came back as a histiocytoma, I would be focusing on the good news that Tate doesn't have a malignant mast cell tumor. And removal and lab analysis of the tumor was the only way you could have gotten that news. Hope this helps!

Since both the tumors were low grade and have not yet metastasized there is no indication to worry about an abbreviated life span at this time. Since your dog is so young and has already had 2 MCTs he will likely have more pop up in the future. It's important to have any little lump or bump you find on him to be checked out by your vet. The sooner they are removed, the less likely they are to spread.

Poor Precious! I know you are worried about you! Good news is that most mast cell tumors are easily distinguished on an fine needle aspire (FNA). The chances of it being a mast cell tumor is less likely but not completely ruled out. Also, the fact that it hasn't grown much and the cells on the FNA were very similar in size and shape means it is likely benign. I think you are making the best decision to have it surgically removed and tested. Also, it is likely more oval due to some local inflammation secondary to the minor trauma a FNA causes. I hope this helps!