By Dr. Steve Surujbally
Canine cancers continued
Breast Cancers/Tumours
So far we have been dealing with surface tumours/cancers (e.g. Skin Cancers). Let’s now look at some cancers in the more underlying tissues.
Breast Tumours (swellings) are very common in the bitch; and half of these tumours will be cancerous. Often there is a mixture of tumour tissues – e.g. Adenomas, Fibromas, Lipomas – that we had discussed in previous articles. Fifty per cent of the time, these tumours will not be painful, not be inflamed, and grow slowly (benign growths). Once they are surgically excised, they will not recur. On the other hand, the other 50 per cent are malignant. I should mention that, by comparison, the incidence of mammary neoplasms in bitches is three times higher than in women. Actually, half of all tumours in the female dog are mammary (breast) tumours.
The cause of mammary tumours is unknown in all species, except mice. (This is interesting, since we use a lot of mice in human research. The breast tissue of mice is obviously quite different from that of humans and, as such, the cancers can – we know – be virus caused, quite unlike human breast cancers. The knowledge pertaining to the cause(s) of cancer in dogs is hazy. There can be little doubt that hormones play an important role in the development of cancerous growths in the breast. Nevertheless, the precise mechanism between a hormonal imbalance and the actual breast neoplasm is not known. However, one thing is clear: Bitches which have been spayed (ovaries and womb removed) do not get breast cancer. By the way, I should mention, for what it’s worth, research has shown that genetic and nutritional influences on breast cancer have been documented in some human (and mice) breast cancer cases, but not in dogs!
Dogs have usually eight, ten and twelve functioning mammary glands (equally divided on each side). They are separate but still interconnected – by the lymph stream, for example. This means that if one gland (usually the posterior glands) on one side is showing cancer, then it is possible that the adjacent glands on that side might also become cancerous.
That’s why the veterinary surgeon usually excises the adjacent glands as well, especially if a small nodule is felt in the tissue.
Which bitches are most likely to develop breast cancers? Well, as I said above, there seems to be some connection between breast cancer and the hormonal imbalance in dogs. So, if your dog is ‘intact’ (with womb/ovaries), mammary tumours/cancers are possible.
If we take out the ovaries before the bitch comes into her first ‘heat’, the risk of breast cancer is dramatically reduced. (NB: There is no improvement relative to the possibility of the bitch getting breast cancer, if we spay her after she is mature). In my experience middle-aged and older dogs tend to be stricken more with breast cancers.
Lastly, allow me to emphasise that cells for breast cancers tend to disassociate themselves from the mother mass and deposit themselves in other organs (metastasis) especially the lungs. For this reason, an X-ray of the lungs may be advisable. Furthermore, as an owner of a female dog, it should be part of your routine to have your middle-aged bitch’s breast examined by your Veterinarian once every three months, if not more regularly. Any time you feel even a small bump in the dog’s breast, rush quickly to your Vet.
Don’t let’s fool around with this ailment. Radical surgery is indicated more often than not. Please don’t be afraid of surgery. The more you postpone the surgery, the more surgical damage has to be done, since a much larger mass has to be removed. The role is: once you feel a lump in the breast, discuss the matter with your vet — with the intention of removing the lump.
Next week we will deal with some other types of prevalent cancers in dogs, and a brief recap of the articles on cancer so far.
