As I've noticed mast cell tumors issues have grown in number of pug cases, I've done some research and the following should answer a pug owner's concerns:
Hello Dr. Richards, I read through the Dogs/Cancer section, which was very informative, but I still have a couple of questions for you. I have an 8 month old, fixed (he was fixed at 6 months), male pug named Odie. He's healthy in every way except about 2-3 months ago I noticed a growth on his foot, it didn't seem to bother him so I didn't really think too much of it, but kept an eye on it. It didn't get any bigger but it didn't go away either so I brought him to the vet & we decided to have it removed. The growth was no more than 1/4 of a cm & the vet removed a considerable amount of skin around the growth. We just got the pathology back on Monday & the vet explained that the growth was a stage 1 mast cell tumor. The tissue around the tumor was free of cancer cells. I'm concerned that because of the location of the tumor, not enough tissue below it was removed, the tumor was in a location equivalent to the top of a human's foot. My questions are: -How serious is a stage one mast cell tumor? (would it be possible to compare it with a cancer in human's such as melanoma?) -Should we have the vet do bloodwork, lymph node aspirate, or abdom. ultrasound to make sure the cancer hasn't spread? (bloodwork done 2 months ago, when he was fixed, was normal) -What type of follow up should we be doing? (bloodwork, etc.) -Would it be wise to have Odie on Prednisone? or would that weaken it's effectiveness in the case of possible future tumors? -Because of the location of the tumor & the results of the pathology, do you feel enough tissue was removed or should we have more tissue removed below the area of the tumor? -Should we be more concerned about the tumor because of Odie's age (we noticed the growth when he was 5-6 months old)? -Is there any information on reoccurrence of stage 1 mast cell tumors? Could this be a one-time thing? -Should we consult with an oncologist? -What do these tumors usually look like (on the skin)? I realize I've asked a lot of questions, I'm very concerned about the health of my dog! We love him soo much. I also feel that the questions I've asked could be of help to others. I sincerely appreciate any information you can give me on the above & any other websites/books I could look at for more information.
THANK YOU!!! Sincerely, Angela
Tumors are classified in two ways. Staging is a way of classifying how far a malignant tumor has spread prior to diagnosis. Grading is a way for the pathologist to give his or her impression of how aggressive a tumor is likely to be (how likely it is to try to spread to other tissues).
There are different staging schemes, but the standard is probably the World Health Organization staging, even though it is geared more towards humans. A slightly simplified version of this is: Stage 1 -- tumor is solitary, no sign that it has spread, tissue margins are clean on removal Stage 2--- the tumor has invaded regional lymph nodes Stage 3--- the tumor is widely invasive (invaded past surgical excision) or there are multiple tumors, even if the lymph nodes are not involved Stage 4-- the tumor has invaded tissue far from the original site, such as the spleen, in the case of a skin tumor
Staging is done by your veterinarian. Physical exam findings, X-rays, bone marrow examination, complete white blood cell counts, buffy coat smears (the buffy coat is where white blood cells accumulate when blood is centrifuged in a tube) and lymph node aspirates may all be useful in staging mast cell tumors. You should be sure that some attempt is made to stage this tumor accurately.
Grading is somewhat subjective and is partially the pathologist's opinion, although there are guidelines for grading, too. Grade 1 tumors are the least likely to be highly malignant and Grade 3 are the most likely to be malignant.
The problem with a tumor located on the foot or lower limbs is the difficulty removing enough tissue under the tumor, just as you mentioned. It is reassuring that the section of the tumor the pathologist examined had no tumor cells beyond the margins but unless it was possible for the pathologist to accurately judge all sections of the tumor that might have had contact with surrounding tissue it is hard to be sure that this assessment applies to the entire tumor margin.
The prognosis for a Grade 1, Stage 1 mast cell tumor responding completely to surgical excision is good. Around 90% of dogs are reported to have long term survival after this diagnosis in most of the studies done on mast cell tumors. This has to be considered in your decision making but there is some room to worry and I would think it would be a good idea to ask your vet to refer Odie to an oncologist or to at least consult with an oncologist about what to do next. There is a lot of ongoing work on chemotherapy for mast cell tumors and radiation therapy can be helpful in cases in which it is questionable whether adequate tissue could be removed from underneath a tumor.
Prednisone is variable in its effects on prognosis following mast cell tumors, with positive responses seeming to run about 20%. Due to Odie's age I would tend to lean towards doing some other sort of follow-up treatment but your vet or the oncologist may have another opinion on that.
Mast cell tumors are very variable in appearance. They are tumor most often used to illustrate why it is possible to justify having almost any skin tumor examined by a pathologist.
I am not aware of any prognostic factors that hinge just on the age of the patient. I think that staging and grading are the most reliable indicators of prognosis.
Hope this helps some.
Info via Vet Info
. Check the page for further mast cell tumor details.
Mike Richards, DVM 6/23/ 2000