Symptoms of Canine Lymphoma
The symptoms of lymphoma usually commonly mimic the symptoms of many other diseases or disorders. Most owners of dogs with multicentric or disseminated lymphoma first find pronounced enlargement of the lymph nodes on the underside of their dog’s neck, beneath and slightly behind the chin. These are the submandibular lymph nodes (the mandible is the lower jaw bone). Affected dogs normally do not seem painful when their submandibular lymph nodes are palpated and show no other unusual symptoms. Other signs that owners may notice include one or more of the following:
- Lethargy (profound)
- Exercise intolerance
- Weight loss
- Loss of appetite (inappetance; anorexia)
- Dark tarry stool (melena; digested blood showing up in the stool)
- Distended abdomen
- Abdominal discomfort
- Increased thirst and intake of water (polydypsia)
- Increased volume of urinate (polyuria)
- Difficulty breathing; shortness of breath (dyspnea)
- Difficulty swallowing
- Skin nodules or masses (single or multiple)
- Skin scaling
- Bruised or ulcerated skin lesions
- Hair loss (alopecia; uncommon)
- Itchiness (pruritis; uncommon)
- Neurological signs: circling, disorientation, lack of coordination (ataxia), seizures, behavior changes, vision abnormalities
Multicentric lymphoma - usually shows up first as painless but enlarged peripheral lymph nodes. Owners may see or feel these in areas under the jaw, in the armpits, in the groin area or behind the knees. Enlargement of the liver and/or spleen can also occur, causing the abdomen to distend. This is the most common form of lymphoid cancer in dogs.
Gastrointestinal (alimentary) lymphoma - is a malignant form of cancer that can show up anywhere along the gastrointestinal tract (stomach, small intestine, large intestine, rectum). Clinical signs of gastrointestinal lymphoma include vomiting, diarrhea, weight loss, lethargy, depression, diarrhea and melena. Low serum albumin levels and elevated blood calcium levels commonly accompany alimentary lymphoma, although these can only be detected by veterinary evaluation of blood samples. This is the second most frequent form of lymphoma in dogs.
Mediastinal lymphoma - where the cancer is localized to tissues in the chest cavity - can cause fluid to build up around the lungs. This can lead to coughing and labored breathing (dyspnea), mimicking the signs of congestive heart failure.
Lymphoma of the skin (cutaneous lymphoma) - is uncommon in dogs. When it does occur, it usually shows up with hair loss (alopecia) and visible bumps on the skin. It can also be itchy (pruritic) and vary widely in appearance, ranging from a single lump to large areas of bruised, ulcerated and/or hairless skin.
Lymphoma of the central nervous system (CNS) - is very uncommon in dogs. When lymphoma is localized in the CNS, dogs typically present with neurological signs such as circling, seizures, behavior changes and incoordination.
Dogs at Increased Risk
Lymphoma is most common in middle-aged to older dogs, although dogs of any age can be affected. There is no recognized gender predisposition for this disease. However, some breeds reportedly have an increased risk of developing lymphoma, including the Golden Retriever, Basset Hound, German Shepherd, Boxer, Scottish Terrier, Airedale Terrier, Bulldog, Poodle and Saint Bernard. A strong familial association has been established in some lines of Bull Mastiffs, Rottweilers and Otter Hounds. Pomeranians and Dachshunds reportedly have a decreased risk of developing lymphoma. The reasons for these breed differences in risk of lymphoma development are not well understood.
There may be an association between canine lymphoma and exposure to certain environmental herbicides, household or agricultural chemicals, smoke and/or electromagnetic radiation, although the reason for the connection remains unclear. Dogs living in industrial areas where paints, solvents or other chemicals are common tend to have a higher incidence.