Lymph nodes are found throughout the body: under the skin, in the chest and in the abdomen. These are the same "glands" that people can feel under their neck when they have a sore throat.
The tonsils form part of this network and swell up if fighting a throat or mouth infection. They are all part of the lymphatic system responsible for keeping the body protected against infections. Lymph nodes react to infections/inflammation and are the body's first line of defense.
Unfortunately, in humans and cats and dogs, we see a cancer of the lymph nodes called Lymphosarcoma (LSA) or Hodgkin's Disease. In cats, it is usually caused by a virus called Feline Leukemia Virus (FeLV) which is preventable using a vaccine. In dogs and humans, the cause of LSA is not known.
Sometimes, LSA does not just cause swelling of the lymph nodes. It can appear as a solid tumour of a body organ (e.g. kidneys, intestines, liver) and in some cases it involves the bone marrow causing a leukemia.
Other possibilities for swollen lymph nodes include a response to overwhelming infections and irritable skin problems e.g. severe flea allergy dermatitis.
LSA can develop in any age pet, but is generally seen in younger animals.
Symptoms vary depending on which part of the body is involved.
A cat may present for acute kidney failure or bowel obstruction due to LSA of the kidneys or intestines respectively. LSA of the eyeball can present as an "angry inflamed eye". If the bone marrow is involved, the pet can deteriorate very quickly and be very sick.
The classic LSA involves swollen lymph nodes. Initially, an owner may just notice the pet has swollen glands and is slightly off colour.
As the disease progresses rapidly, there is a quick deterioration in the pet's health with euthanasia usually performed within 3-6 weeks of initial diagnosis if no treatment is given.
A diagnosis of LSA is made by removing an entire lymph node (usually the one behind the knee/stifle) under general anaesthesia and submitting it to a pathology lab for analysis. Sometimes, a meaningful result can be obtained from a needle biopsy of a swollen gland, but pathologists in general prefer a whole lymph node to look at.
LSA can be classified according to its distribution in the body and whether or not the bone marrow is involved. This system can sometimes help the vet in giving a more accurate prognosis.
Chemotherapy using combinations of different drugs can be quite successful in getting rapid reduction in the size of the body's lymph nodes. However, the trick is in keeping the LSA from re-occurring. In veterinary medicine, we don't use the very high doses of chemotherapy used in humans so serious side effects like hair loss are not so common. None the less, regular blood tests and monitoring for other side effects is essential.
Because chemotherapy drugs can cause serious illness in people who accidentally come in contact with them (e.g. needle stick injury, squirted some in to the eye) all waste material has to go into a special waste unit for proper disposal. Staff involved in handling the drugs have to gown up , double glove, wear masks and safety eye wear. The drugs can be very expensive as well. As a result, most vet refer these cases to a specialist centre which is geared up for treating such cases.
All in all, treatment for LSA is very involved, expensive and requires total commitment from the owner. Life expectancy can be increased by several months and some cases go onto full remission.