Cancer Part 2: Lymphoma

In the previous post we discussed lymph nodes as common places for cancer to metastasize to, but there can also be primary cancer of the lymphatic system.  This is known as Lymphoma or may sometimes be called Lymphosarcoma.   Dogs with Lymphoma (LSA) commonly present with the complaint of lumps, swellings or masses around the head and neck.  These are the submandibular and prescapular lymph nodes that the owners are feeling as they pet or groom their dog.  The diagram below shows the locations of the external lymph nodes you can feel in a dog.

Typically, once the veterinarian examines the dog they will find that most or all of the above nodes are enlarged.  There can be two reasons for this 1) systemic illness or infection (remember the lymph nodes clean or drain infection away from the cells) or 2) cancer of the lymph nodes=lymphoma.

Diagnosis can usually be made by cytology/fine needle aspirate but sometimes a surgical biopsy is needed.  Note than most dogs are feeling fine at the time of diagnosis.

This is what a cytology of lymphoma looks like

I tried to find a normal lymph node for comparison but that was harder than anticipated.

Enlargement of the lymph nodes is the most common form of LSA accounting for greater than 80% of cases.  Cutaneous (skin), splenic, intestinal and other extra-nodal forms make up the rest.  Lymphoma is one of the most common canine cancers and occurs in an estimated 24/100,00 dogs annually. 

While LSA typically affects middle aged to older dogs, this disease does not discriminate against age.  I have diagnosed dogs as young as 2-3 years old.  That's really not something you want to do-people do not expect their tail-wagging two-year old dog to be diagnosed with a terminal illness.  Breeds with increased incidence include Boxers, Bassets, St. Bernards, Airedales, and Bulldogs. 

LSA is a rapidly progressive disease.  Without treatment survival times are approximately 1 month.  Treatment options include prednisone, single agent chemotherapy or multi-drug chemotherapy.  Prednisone alone can extend survival to 2-3 months.  This is a very inexpensive option for owners who don't want or are unable to pursue traditional chemotherapy.  Multi drug protocols are the most successful with 60-80%  of dogs obtaining remission. There are a variety of protocols available, many of which involve weekly or twice monthly treatments sometimes with oral medications given daily.  These protocols can involve a significant time and financial commitment on the part of the owner but can achieve survival times of up to 12 months. 

Cats
Incidence of feline lymphoma is estimated to be 200/100,000 annually.  Feline lymphoma is not typically limited to the nodes but can include internal organs, intestines, blood and bone marrow.  A significant amount of cats with lymphoma are Feline Leukemia positive.  Radiation therapy is appropriate for certain forms of lymphoma with multi drug chemo protocols being used for the rest.  Remission rates are approximately 60% with an average 40 week survival time.