A. I am very sorry to hear about the loss of your sister's dog due to lymphoma. Cancer really is the silent, stalking killer. It leaves very little trace of its existence until it's too late. Blood tests and X-rays usually appear normal, until the disease is very advanced.

Just like with human medicine, new research is needed to develop methods of early detection. Very vigilant dog owners can pick up on early signs of cancer. Remember, cancer usually affects older dogs, but not always. It's the No. 1 cause of death in dogs (in humans the No. 1 cause of death is heart disease).

With lymphoma, your dog's lymph nodes may become enlarged, and you would feel large, marble-like masses under the jaw. You might notice a loss of energy, or a decrease in appetite. All dogs throw up once in a while, but an increase for no apparent reason should be checked out by your vet.

Newer technologies, such as ultrasound and laparoscopy (a noninvasive surgery that allows a veterinary surgeon to look around in the abdomen), have helped with early diagnosis of cancer, but more work is needed. Hopefully, some day blood tests will be developed as an early screening test.

In the meantime, try not to worry about your other dogs. Cancer in general is not considered hereditary (although that is sometimes part of the picture). Enjoy your dogs, and love them until they don't know what to do.