My dog's mast cell tumor report says no mitosis. What does that mean?

A) The likelihood of reoccurrence is higher if the margins are dirty. While it may be categorized as a low grade, it would be helpful to know the mitotic index which is a quantitative measure of mitotic figures observed in the cancer cells. If the mitotic index is high, reoccurrence is more likely. B) If no further treatment is pursued, it may or may not return. C) Prior to any further surgery or treatment you need to have Barney evaluated by a veterinary oncologist to discuss the best treatment options for him.

I would definitely recommend asking your veterinarian to discuss the cytology report with you - he/she is in the best position to interpret the findings for your dog based on the clinical appearance of the mass. But, I can do my best to translate what the report actually says :) Essentially, it says that the pathologist saw several types of normal blood cells (RBCs, platelets, neutrophils, and macrophages) - this is typical for a sample that contained some blood, as many aspirates do from masses that have a good blood supply. The report also says specifically that no tumor cells were seen (which is good!), and that the pathologist suspects that the mass is inflammatory or scar tissue related to some type of injury rather than a tumor. Your veterinarian should be very willing to discuss this with you to see if any further testing or treatment would be recommended for Gracie :)

Mitotic index is defined as the ratio between the number of cells in a population undergoing mitosis to the total number of cells in a population. So your dog's mass' mitotic index being 31/10 (31 mitoses in 10 high power fields) would be (less accurately) fall into the category of >5 mitoses per 10 high power fields. This would mean that a mitotic index of 31/10 HPF designates a high grade malignant tumor.

Thank you for submitting your question regarding Twix. Mast cell tumors are one of the most common forms of skin cancer in dogs. If the margins were clean (meaning all of the cancerous cells were removed), then the mass should not recur. However, mast cell tumors are one of the more unpredictable types of cancer. I recommend closely monitoring his incision site at home for any regrowth. It is best to see his veterinarian at least every 6 months for an examination. At this visit a thorough physical examination will be performed to search for other masses or enlarged lymph nodes. Blood work should be monitored as well. Unfortunately, there is nothing that you or your veterinarian can do to prevent further growths from forming. If any new new growth is observed, a fine needle aspirate should be performed as soon as possible to determine the type of mass. If it requires surgical removal, it is always best to have it done while small for the best chance of achieving clean margins. I hope this information helps!

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!

Skin grafting can be tricky and there is a high risk that the graft would fail, especially when it is applied to an area where there previously was cancer. Mast cell tumors require 2 to 3cm margins and on the leg, many times, this is unachievable. Amputation is likely the best option. If you want to try and save the leg, I would discuss this further with a soft tissue surgeon and then an oncologist. I hope this helps guide you in the right direction. Please feel free to contact me with any further questions or concerns and I would be more than happy to help you further.

Surgery to remove a peripheral lymph node is not any more invasive than the surgery to remove a mast cell tumor on the skin. I'm assuming this lymph node is one that is near his shoulder or behind his knee. This could provide valuable information, because additional treatment would be recommended if cancerous mast cells are confirmed in the lymph node even though the initial biopsy came back as a low grade tumor that is less likely to spread. You can always ask your vet about the potential complications of surgery.