Lymphoma (lymphosarcoma) in dogs is a cancer of lymphocytes.
Lymphocytes are white blood cells that play important roles in the immune system. They defend the body from pathogens (infectious agents) and foreign substances.
Types and Symptoms of Lymphoma in Dogs
Lymphoma can develop on any part of the body. The general symptoms of lymphoma in dogs are loss of appetite,
lethargy, weight loss and weakness.
Other specific symptoms depend on where the tumor develops.
Lymphoma in dogs can be divided into 4 main types, based on the location of tumor:
1. Multicentric lymphoma
This accounts for about 80% of lymphoma in dogs.
Location: lymph nodes.
Symptoms: Enlarged lymph node(s) appearing as lump(s). Initially, dogs may experience no pain or minor symptoms. As the tumor grows, it may cause obstruction and damage organ function. Malignant tumor may spread to other organs. Dogs will fall ill and show some of the general symptoms as mentioned above.
2. Gastrointestinal lymphoma
Location: intestinal tract.
Symptoms: vomiting, loss of weight, reduced appetite and diarrhea and abdominal pain
3. Mediastinal lymphoma
Symptoms: breathing difficulty, excessive fluid intake and urination
4. Extranodal lymphoma
Location: skin, kidney, nervous system, eyes, lungs, bone marrow, etc
Cutaneous (skin) lymphoma symptoms: bumps, redness, lesions and itchiness.
See this post on Dog Lymphoma Treatment