I drew this imaginary cat to show a common location of lymphoma in the pets of readers like you who write to me. Those lymphomas often begin in the villi, the nutrient-absorbing structures that line your cat's small intestine. Areas of the small (SI) and upper large (LI) intestine where the problem is often most severe are colored red. S is your cat's stomach. As the problem progresses, normal intestinal walls (Nm) sometimes thicken to the point where your veterinarian can feel them (Abn) (palpate them) through the cat's tummy.

It is quite normal for a good number of non-cancerous lymphocytes to position themselves in the villi to guard against unwanted things that might enter your cat through its intestines. At the top left, I drew a schematic of a single villus and how a moderate number of normal lymphocytes (L) might be scattered through it. In the second image, the number of those lymphocytes has increased above what is normal. That could represent the chronic inflammation of inflammatory bowel disease (IBD) or it could represent early lymphoma. In the third image, excessive numbers of lymphocytes are present. It is the difficult job of the veterinary pathologist to decide at what point those transitions to cancer have occurred. Molecular techniques I discussed in the article help veterinarians make that decision.

You can follow a cat with lymphoma, Sam, through his diagnosis and treatment at one of the World's most sophisticated veterinary facilities here.

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