...he always scrambled from the car and pranced through your door with a smile on his face. In his view every visit to you was a party with friends.
Stop by and visit Hope Veterinary Specialists at Springfest 2016 at Devon Veterinary Hospital (Across from Devon Fairgrounds)
Cancer in Pets
Cancer affects all of us, whether through a family member, a close friend, a teacher or a beloved pet. There are approximately 165 million dogs and cats at risk for cancer in the United States. This translates into nearly 4 million dogs and 4 million cats developing cancer each year. It is estimated that nearly 50%of all dogs and 32% of all cats over the age of 10 will develop cancer, making it the leading cause of death in our pets.
The term cancer describes a large number of diseases with the common feature of uncontrolled cell growth. The development of cancer depends on multiple factors. Environmental and genetic contributions often result in an accumulation of errors in the cell leading to uncontrolled growth. Breed, gender, and environmental factors all play a role in the development of cancer.
Warning Signs of Cancer in Pets
Early cancer detection is associated with best outcomes and in many cases a cure. It is important for owners to accurately recognize possible “warning signs” of cancer in their pets. If noted, it is important to contact the primary care veterinarian for a thorough examination.
- Lumps and Bumps
Not all lumps and bumps on or under the skin are cancerous. It is important to bring this to the attention of your primary care veterinarian to further investigate. A needle aspirate or biopsy are routine procedures to help determine benign from malignant. Needle aspirates are painless, typically do not require sedation or anesthesia, and often reveal the underlying cause of the skin lump. In some cases, a needle aspirate cannot be performed and a biopsy under light sedation or general anesthesia may be recommended.
- Abnormal Odors
Offensive odors from your pet’s mouth, ears, or any other part of the body, should be checked out. Oftentimes cancers of these regions can cause foul odors as a result of secondary infections. Tumors, unlike normal tissue, are more susceptible to infection especially when located in certain areas of the body such as the mouth, the ears and around the anus. A thorough physical examination can often determine the location and cause of the odor.
- Abnormal Discharges
Abnormal fluid discharge from any part of your pet’s body should be checked out by your veterinarian. Some cancers may produce fluid while others may put pressure on the normal drainage system in the body leading to a backup of fluid. A thorough physical examination can often determine the location and cause of the discharge.
- Non-Healing Wounds
If your pet has wounds or sores that are not healing, it could be a sign of infection, skin disease, or cancer. Unlike normal tissue which has the ability to heal itself, tumors do not contain this property and to the pet owner, this may appear as a non-healing wound. An examination and tissue sample can often determine the underlying cause.
- Weight Loss
Cancer can cause weight loss in a pet. If sudden weight loss is noted in your pet this should be evaluated by a veterinarian. Cancer may prevent normal intake of food or cancer can compete with the body for important nutrients, leading to weight loss. A thorough physical examination, routine laboratory diagnostics and in some cases imaging (radiographs or ultrasound) may be required to determine the underlying cause.
- Change in Appetite
Pets generally do not stop eating without an underlying reason. A recent lack of appetite could be a result of underlying cancer and should be evaluated. Cancer may affect normal intake of food through either the development of nausea or the physical presence of the tumor (oral cavity of teh gastrointestinal tract).
- Coughing or Difficulty Breathing
Coughing or changes in breathing can be a result of heart disease, lung disease, or cancer. If this is noted your pet should be evaluated by your veterinarian. Cancers located within the respiratory system can affect the normal respiration process, resulting in changes in breathing and/or a cough. A thorough physical examination with special emphasis on the respiratory system through auscultation is warranted. In some cases, chest x-rays may be required to visualize the chest cavity in more detail.
- Lethargy or Depression
If you notice your pet is less active, sleeping more, or less interactive, these can be signs of cancer and should be evaluated further. Cancer, depending upon the type and where it is located, may result in minor discomfort or affect normal exercise which may manifest as lethargy and/or depression.
- Changes in Bathroom Habits
Changes in your pet’s urinary or bowel habits may be potential signs of cancer. Straining to urinate or defecate, blood in the stool or urine, more or less frequent eliminations, are some symptoms of cancers located in the urinary or gastrointestinal system. An examination, routine diagnostics and often more advanced imaging such as an ultrasound are often required to properly assess the cause of these symptoms.
- Evidence of Pain
Limping or other evidence of pain is generally more likely associated with arthritis or muscular injury, but it can also be a sign of cancer (especially cancer of the bone) and should be evaluated by your veterinarian. A routine physical examination and gait evaluation can often localize the region of the body from which the lameness is occurring. Radiographs of the affected area can often help elucidate the underlying case.
Case: Kissy, a nine-year-old, female spayed Labrador Retriever presented to her local veterinarian for foul smelling breath. She had been previously healthy with the exception of a cranial cruciate rupture that had been successfully repaired when she was 7 years of age. Other than her foul breath she was clinically healthy. On examination, she was found to have moderate erythema of her gums diffusely, with moderate tartar. Based on a working diagnosis of stomatitis she was treated with a 14-day course of an antibiotic (clindamycin). Initially, she responded well with improvement of the odor from her mouth, but the gingival erythema did not improve. Over the next month, Katie’s red gums progressed and she developed an area on the external portion of her left lower lip, which was erythematous and ulcerated.
Given the progression of the lesion(s) the decision was made to biopsy the area on the lip. The biopsy revealed epitheliotropic lymphoma.
Epitheliotropic lymphoma is a form of lymphoma. However, instead of involvement of the lymph nodes, liver, spleen and bone marrow, dogs (and rarely cats) with this disease usually get a diffuse involvement of the skin, oral mucosa or both. On histopathology, malignant lymphocytes, usually, T-cells, infiltrate within the layers of the epithelium, either the skin or oral mucosa, which is why the disease usually starts as erythema and slowly progresses to plaques and nodules (Moore et al Vet Derm 2009). Eventually, the disease can spread to lymph nodes and to the peripheral blood. It is also known as mycosis fungoides.
The majority of dogs with epitheliotropic lymphoma have a diffuse form of the disease and chemotherapy using CCNU (lomustine) has been shown to result in responses in some dogs, but long-term control of the disease is uncommon with control times of 2 t o6 months published (Risbon et al, JVIM 2006, Williams et al JVIM 2006).
However, a subpopulation of these dogs will have involvement of the oral mucosa only. In these cases, radiation therapy may also be of benefit as it may be effective against the local tumor. Radiation therapy for this disease can involve either a definitive protocol involving 15 to 20 treatments delivered daily, or palliative radiation involving between 3 and 6 treatments over a three week period. Typically the radiation will need to be directed to large portions of the mouth, so side effects can be significant. However, these side effects can be managed well with anti-inflammatory and pain medications. Palliative protocols usually result in much less significant side effects.
Tumor control with radiation is not well defined yet and there are no true reports of the effectiveness that have been published.
However, local tumor control following radiation is very common with long-term tumor control in some dogs.
Kissy was treated with a course of palliative radiation involving 6 treatments delivered twice a week to the oral cavity and the local lymph nodes. Moderate erythema developed within the radiation field but resolved within 2 weeks of the end of treatment. Her owners decided not to pursue chemotherapy based on concerns about her quality of life.
The area of erythema and ulceration resolved following radiation and has been in remission for approximately 6 months.
Submitted by Dr. John Farrelly DVM, MS,
ACVIM (Oncology), ACVR (Radiation Oncology)
Radiation Oncologist/Medical Oncologist at The Veterinary Cancer Center
Moore PF, Affolter VK, Graham PS, Hirt B. Canine epitheliotropic cutaneous T-cell lymphoma: an investigation of T-cell receptor immunophenotype, lesion topography and molecular clonality. Vet Dermatol. 2009 Oct;20(5-6):569-76.
Risbon RE, de Lorimier LP, Skorupski K, Burgess KE, Bergman PJ, Carreras J, Hahn K, Leblanc A, Turek M, Impellizeri J, Fred R 3rd, Wojcieszyn JW, Drobatz K, Clifford CA. Response of canine cutaneous epitheliotropic lymphoma to lomustine (CCNU): a retrospective study of 46 cases (1999-2004). J Vet Intern Med. 2006 Nov-Dec;20(6):1389-97.
Williams LE, Rassnick KM, Power HT, Lana SE, Morrison-Collister KE, Hansen K, Johnson JL. CCNU in the treatment of canine epitheliotropic lymphoma. J Vet Intern Med. 2006 Jan-Feb;20(1):136-43.
History: An 8-month-old male intact Rottweiler presented to his rDVM for evaluation of acute onset of right hind limb (RHL) lameness following a traumatic blow while playing with another dog. Radiographs of the affected limb were normal. The problem was managed conservatively with controlled activity and carprofen, 75mg PO BID for 2 weeks. The lameness progressed to metacarpal knuckling and dragging of the leg. The patient was referred to a neurologist for further evaluation. A neurologic exam localized a lesion to the T3-L3 region with lateralization to the right side. The remainder of the exam was unremarkable. Initial staging tests were done: CBC and chemistry were within normal limits. A lumbar CSF tap was done and results showed a normocellular sample with a mildly elevated protein level (71mg/dL). No other cytological abnormalities were detected. A myelogram was done next and revealed a contrast filing defect at L1-L2 with a classic “golf-tee” sign consistent with an intradural-extramedullary mass localized to the right (image 1 and 2). A right-sided hemilaminectomy (L1-L2) was done and the intradural mass was removed piecemeal. Histopathology revealed a primitive complex neoplasm comprised of both epithelial and mesenchymal components organized into tubular and glomeruloid structures. There were 5 mitoses/HPF within the mesenchymal component. The mass was noted to be invading the nerve root and white matter and margins were incomplete (images 3-4). Immunohistochemistry was done with a panel of markers and was negative for chromogranin, neurofilament, neuron-specific enolase and glial fibrillary acidic protein. However, the samples were positive for cytokeratin and Wilm’s gene product (WT1) confirming the diagnosis of an incompletely excised nephroblastoma.
Two weeks after neurosurgery, the patient was referred to the oncology service to discuss prognosis and treatment options. The patient presented ambulatory x 4 but exhibiting marked difficulty in rising and a frequent “bunny hopping” gait. There was also significant muscle atrophy in the hind end (R>L). Neurology exam revealed mild bilateral hindlimb ataxia and paraparesis (R>L) with moderate scuffing of the nails of the RHL. Conscious proprioception was absent on the RHL and delayed on the LHL. But strong withdrawls remained intact. No ataxia or paresis was noted in the thoracic limbs and conscious proprioception in thoracic limbs was also normal. Panniculus and perineal reflexes were intact and spinal palpation was unremarkable. Further staging diagnostics included thoracic radiographs and abdominal ultrasound which were both within normal limits, as well as lateral thoracolumbar radiographs and CT and MRI scans for treatment planning (images 5 and 6).
The MRI showed mild soft tissue swelling with the presence of an autogenous fat graft as well as cord compression and invasion by a hyperintense lesion.
Treatment options were discussed as being limited to radiation therapy and a guarded prognosis was given. The owners elected to proceed with definitive radiation therapy. A CT scan was obtained for treatment planning (image 7). The plan was to administer 16×3 Gy fractions to a total of 48Gy via parallel, opposed treatment portals . Prednisone was started at 20mg PO SID. Treatment proceeded uneventfully with relatively stable clinical signs. By 6 weeks post treatment, the patient presented for a recheck and was reportedly showing markedly improved strength in his hind end. He was still showing difficulty in rising with a mild bunny hopping gait but the muscle atrophy was resolved and the CPs were decreased but intact on the RHL and normal on the LHL He was weaned off of the prednisone at this time. At a 3 month recheck, the patient continued to show improved strength. He was rising with more ease, no longer exhibiting nail scuffing and was able to jump up on his hindlegs with completely normal hindlimb CPs. The patient continued to do very well up to a year post radiation therapy when he was lost to follow-up.
Spinal nephroblastoma in dogs is a very rare disease. Most reports in the veterinary literature are of patients euthanized after imaging or shortly after surgical exploration. Surgery alone is reported to result in survival times of 71 days 1. One report of cytoreductive surgery and radiation reported survival times up to 560 days 2. In people, Wilm’s tumor is the most common primary malignant renal tumor of childhood. They are histologically diverse with blastalemal, epithelial and stromal components (not all present in each case). Prognosis is dependent on stage and histologic differentiation (anaplastic being worse). In dogs, nephroblastomas can affect spinal or renal tissues. The spinal tumors have a debatable histogenesis in dogs (neural rests vs ectopic renal blastema), however, histology, immunohistochemistry and a virtually uniform spinal involvement at T10-L2 argue more strongly for a renal origin of these tumors. Metastasis is reported to occur in the spine, bone marrow, lung and liver 3.
1: Spinal cord nephroblastoma in dogs: 11 cases (1985-2007). Brewer DM. et al. J Am Vet Med Assoc. 2011 Mar 1;238(5):618-24.
2: Canine spinal nephroblastoma: long-term outcomes associated with treatment of 10 cases (1996-2009). Liebel FX. Vet Surg. 2011 Feb;40(2):244-52.
3: Possible Intraspinal Metastasis of a Canine Spinal Cord Nephroblastoma. Terrel SP. et al. Veterinary Pathology January 2000 vol. 37 no. 1 94-97.
Image 1: “golf tee” filling defect
Image 2: “golf tee” filling defect
Image 3: Tubular structures
Image 4: Glomeruloid structure
Image 5: CT image post laminectomy, pre-RT.
Image 6: Post laminectomy MRI; white line denotes position of fat graft and region of cord invasion.
Image 7: RT planning (bilateral opposed fields)