Heart Tumors and Cancers in Dogs

Heart tumor in Rottweiler,Chemodectomas, Heart-lung bypass machines

Question: Thank you, Dr., I've asked for a further clarification as some Dr.'s feel it was more likely a chemodectoma rather than a pheo. They feel you can't call it a pheo if the adrenal glands were not examined. I don't find mentin of the adrenal glands in the clinical pathology report. I have asked the pathologist to do a immunoperoxidase stain for a more definate diagnosis. In any event, It seems that heart tumors are not operable in dogs, malignant or benign. Is it also true that dogs don't do well on heart/lung bypass machines , are you aware of any such successful surgeries? This is purely informational, I can't help but wonder if we caught this was there any possibility it could have been localized and removed. My mother , a few years ago, had a myxoma in her right atrium. It was successfully removed , however, I'm not sure the same methods are available for our canine patients. Thank you again, for your response. I know when I'm ready I will get another Rott as we found him to be a pure joy. He was highly socialized and never displayed any temperment disorder . My 9-year old son is also deeply devastated by his death, we miss him terribly and 5 weeks later it just seems that he is so irreplaceable. He was our first Rotweiller and now I'm sold on the breed. It's a pity that this breed is so misunderstood.

Answer: Mindy-

I know that there are veterinary surgeons using heart-lung bypass machines to perform heart surgery (Dr. Lynn Boggs in Texas does this in private practice, even). This work is in the early stages and there are still a lot of failures. Enough that it is probably not untrue to say that dogs have not done well, so far, with the use of these machines, in real practice. Some of the cardiac surgical techniques used in people were worked out with dogs and I am assuming that some of those dogs must have done well. The difference there could really be that the persons doing the work were experienced cardiac surgeons and support staff familiar with the operation of the bypass machines --- something that just barely exists in veterinary medicine. However, there are also some success stories in dogs. So I don't think that it is true that dogs do not tolerate this procedure at all, but I do think that it is reasonable to say that it has problems for canine patients at the present time.

I do think that it is true that heart based tumors don't seem to respond very well to surgery, based on the current surgical techniques, although sometimes there is improvement and sometimes removal of the pericardium allows for palliative treatment -- allowing the tumor to co-exist with the patient for longer than it would have otherwise, but usually this doesn't provide a long term solution if cancer is present around the heart.

Chemodectomas are tumors of the chemoreceptive organs and occur most often in the aortic and carotid bodies. A tumor in the chest is usually in the aorta and one in the neck region in the carotid artery. I am not sure how much they resemble pheochromocytomas on histopathologic examination but it wouldn't surprise me if they were hard to tell apart. The preferred treatment for these, when they can be identified early, is surgery. There is at least one report of successful radiation therapy for a tumor too large for surgery but not all dogs respond to radiation. Short nosed dog breeds (boxer, Boston terrier, bulldogs) are supposed to be prone to these but I have not seen any specific reference to rottweilers. Dogs with this condition affecting the aorta are supposed to develop signs of right sided heart failure that can lead to the diagnosis. I do not know how frequently sudden or rapid death occurs with this tumor type.

I hope that this is helpful.

Mike Richards, DVM 8/13/2001

Pheochromocytomas

Question: Dr. Richards, I now have a finding back from the necropsy, I've been told that my dog had a Pheochromocytoma,not the hemangiosarcoma that was discussed earlier.

I asked the Dr. if he thought that was the cause of death and he responded, probably so. It appears to be a rare but deadly tumor that is not usually seen or even correctly diagnosed in humans. Just prior to the cardiac arrest, my dog did have an erythmia, and of course the vomitting prior to seizure. Do you have any thing along the line of a case history that we could discuss. This is such a rare tumor and now I'll never know if it was the primary site. I have been told it was malignant and that little could of been done even with early detection. I would think this tumor would have caused the overproduction of hormones - that may explain the high blood sugar, but no weight loss was noted, only the vomitting and one other episode of nausea in mid February. Thank you.

Answer: Mindy-

Pheochromocytomas are tumors of the adrenal gland. They produce the adrenal hormones norephinephrine and epinephrine, the common name of which is adrenaline -- the hormones secreted in stressful situations. These hormones can dramatically raise blood pressure and can result in sudden death, or can make death more likely when anesthetics must be used, because epinephrine predisposes patients to arrhythmias when using halothane or isoflurane anesthetics.

These tumors are very hard to detect because they do not cause clinical signs that are distinctly related to the tumor alone. They cause clinical signs such as weight loss, decreases in appetite, weakness, fainting and pale mucous membranes (gum and eye color), which can occur with many other conditions. A more specific sign that is sometimes seen is a tachyarrhythmia (rapid uncontrolled heart rate), sometimes with a rapid respiratory rate at the same time. Unless there is a reason to suspect these tumors they are usually found by accident.

In dogs, about one-third of pheochromocytomas are malignant (spread to far away sites) and they can be aggressive locally (invading tissue around the adrenal gland). Surgical removal is often possible and it can result in a long term cure if the tumor has not spread. In cases in which the tumor has spread, there is no treatment protocol that I am aware of that will cure a dog, although there may be some response to chemotherapy (some increase in the expected life span with treatment) and it is possible to treat the hypertension and alleviate some of the clinical signs by doing that.

I have not seen any references to rottweilers being prone to these tumors in the literature but I am aware of more cases in rottweilers than in any other breed -- but then we own rottweilers, so I might just be paying more attention to cases in this breed.

I hope that this information is helpful. If it raises more questions please feel free to ask them.