CANINE
This section focuses on the fundamentals of canine oncology, providing in-depth insights into the diagnosis, treatment, and management of common cancers in dogs. Explore key topics such as lymphoma, mast cell tumors, osteosarcoma, hemangiosarcoma, and more.
The notes include essential information on tumor biology, staging systems, advanced diagnostic techniques like cytology and histopathology, and treatment modalities such as surgery, chemotherapy, and radiation therapy.
Notes:
Canine and Feline Osteosarcoma
Osteosarcoma (OSA) is the most common primary bone tumor in dogs and, although less frequent, it is also reported in cats. This malignant neoplasm is highly aggressive, locally invasive, and characterized by an almost inevitable metastatic potential, most commonly to the lungs. In dogs, OSA predominantly affects large and giant breeds and tends to arise in the metaphyseal regions of long bones, particularly the distal radius, proximal humerus, distal femur, and proximal tibia. Cats are less commonly affected, but their disease course is often slower and metastasis occurs less frequently than in dogs. Clinical signs typically include progressive lameness, pain, swelling, and, in advanced cases, pathologic fractures. Accurate diagnosis and staging are essential, as treatment strategies and prognosis depend heavily on tumor location, presence of metastasis, and systemic involvement.
Canine Multiple Myeloma
Canine multiple myeloma is a malignant plasma cell neoplasm affecting primarily middle-aged to older dogs, characterized by monoclonal gammopathy, osteolytic bone lesions, and Bence-Jones proteinuria. Neoplastic plasma cells proliferate in the bone marrow and secrete excessive immunoglobulins, often leading to hypercalcemia, renal impairment, and hyperviscosity syndrome.
Clinical signs include lethargy, bone pain, PU/PD, and bleeding or neurologic deficits. Diagnosis requires identification of a monoclonal spike on electrophoresis, plasmacytosis, and radiographic bone lysis. Treatment involves melphalan with corticosteroids, supportive care, and bisphosphonates. Remission is common, but long-term control depends on systemic involvement and therapeutic response.
Canine Transitional Cell Carcinoma
Transitional cell carcinoma is the most common malignant tumor of the canine urinary tract, typically arising in the trigone region of the bladder. It presents with signs mimicking urinary tract infection—stranguria, hematuria, pollakiuria—and may progress to urethral obstruction or metastasis. Diagnosis involves imaging, urine cytology, and definitive confirmation with BRAF mutation testing or biopsy. Treatment is challenging due to tumor location, with options including NSAIDs (piroxicam), chemotherapy, and palliative care.
Canine Lymphoma
Canine lymphoma is a common hematopoietic malignancy, most often presenting as multicentric lymphadenopathy. It typically arises from B lymphocytes and can affect multiple organ systems including lymph nodes, spleen, liver, gastrointestinal tract, and bone marrow. Diagnosis is based on cytology or histopathology, with immunophenotyping (B vs. T cell) providing prognostic value. Treatment of choice is multi-agent chemotherapy (e.g., CHOP protocol), which can induce remission in most cases, though relapse is common.
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NAVLE Flash Cards
Question 1:
A 10-year-old spayed female Scottish Terrier presents with stranguria, pollakiuria, and occasional hematuria. Physical examination is unremarkable except for discomfort on bladder palpation. Abdominal ultrasound reveals a mass at the trigone of the bladder. Which of the following is the most likely diagnosis?
A. Bacterial cystitis
B. Transitional Cell Carcinoma
C. Urolithiasis
D. Prostatic adenocarcinoma
Question 2:
Which of the following is the most appropriate initial treatment plan for a dog diagnosed with non-resectable transitional cell carcinoma of the bladder?
A. Immediate cystectomy
B. NSAIDs (e.g., piroxicam) with or without chemotherapy
C. Long-term antibiotics and dietary therapy
D. Radiation therapy followed by surgical excision
Question 3:
Which of the following correctly describes the typical signalment and location of canine osteosarcoma?
A. mall breed dogs; diaphyseal humerus and tibia
B. Large breed dogs; metaphyseal regions “away from the elbow, toward the knee”
C. Middle-aged cats; appendicular skeleton, distal ulna most common
D. Young cats; axial skeleton only
Question 4:
Which of the following findings most strongly supports a diagnosis of canine appendicular osteosarcoma?
A. Symmetric metaphyseal sclerosis on radiographs
B. Mixed lytic-proliferative lesion with sunburst periosteal reaction
C. Elevated serum calcium with diffuse osteopenia
D. Radiographic evidence of joint collapse and periarticular osteophytes
Question 5:
A 7-year-old Rottweiler is diagnosed with osteosarcoma of the distal radius. What treatment offers the best survival outcome?
A. Limb amputation alone
B. Amputation with adjuvant chemotherapy (carboplatin, cisplatin, or doxorubicin)
C. NSAIDs and opioids for palliative care only
D. Limb-sparing surgery without chemotherapy
Question 6:
Which of the following correctly describes the typical signalment and location of canine osteosarcoma?
A. Small breed dogs; diaphyseal humerus and tibia
B. Large breed dogs; metaphyseal regions “away from the elbow, toward the knee”
C. Middle-aged cats; appendicular skeleton, distal ulna most common
D. Young cats; axial skeleton only
Question 7:
Which of the following findings most strongly supports a diagnosis of canine appendicular osteosarcoma?
A. Symmetric metaphyseal sclerosis on radiographs
B. Mixed lytic-proliferative lesion with sunburst periosteal reaction
C. Elevated serum calcium with diffuse osteopenia
D. Radiographic evidence of joint collapse and periarticular osteophytes
Question 8:
A 7-year-old Rottweiler is diagnosed with osteosarcoma of the distal radius. What treatment offers the best survival outcome?
A. Limb amputation alone
B. Amputation with adjuvant chemotherapy (carboplatin, cisplatin, or doxorubicin)
C. NSAIDs and opioids for palliative care only
D. Limb-sparing surgery without chemotherapy
Answers
Question 1:
Answer: B) Transitional Cell Carcinoma
Explanation:
Transitional Cell Carcinoma (TCC) is the most common malignant bladder tumor in dogs, with a strong breed predisposition in Scottish Terriers, Shetland Sheepdogs, and Beagles. It typically affects older, spayed females and arises most commonly at the trigone of the bladder, although it can involve the urethra and prostate.
Clinical signs are due to obstructive or irritative lower urinary tract disease, such as:
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Stranguria
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Pollakiuria
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Hematuria
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Urinary incontinence
Diagnosis is based on:
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Ultrasound findings (mass at trigone)
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Urine cytology or traumatic catheterization (to avoid seeding with cystocentesis)
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BRAF mutation testing in urine (non-invasive and specific)
TCC must be distinguished from chronic UTI or urolithiasis. Prostatic adenocarcinoma is rare in females.
Question 2:
Answer: B) NSAIDs (e.g., piroxicam) with or without chemotherapy
Explanation:
Surgical resection is usually not feasible for bladder TCC due to the frequent location at the trigone, a critical area that includes the ureters and urethra. The cornerstone of therapy is medical management, especially:
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NSAIDs, particularly piroxicam, which inhibits COX enzymes and has anti-tumor and anti-inflammatory effects.
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Chemotherapy, such as mitoxantrone or vinblastine, is commonly used in combination with piroxicam for improved outcomes.
Radiation therapy may be used in some centers, but side effects to surrounding tissues (colon, rectum) limit its use.
Prognosis:
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Median survival time with piroxicam alone: ~6 months
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Combination therapy (NSAID + chemo): ~10–12 months
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Metastasis to lungs or regional lymph nodes is common in later stages.
Question 3:
Answer: B. Large breed dogs; metaphyseal regions “away from the elbow, toward the knee”
Explanation:
Canine osteosarcoma is most common in large and giant breeds, typically middle-aged to older dogs. Classic appendicular locations include the distal radius, proximal humerus, distal femur, and proximal tibia (“away from the elbow, toward the knee”). Cats are less commonly affected, with slower disease progression and less frequent metastasis.
Question 4:
Answer: B. Mixed lytic-proliferative lesion with sunburst periosteal reaction
Explanation:
Osteosarcoma produces an aggressive bone lesion with cortical lysis, proliferation, Codman’s triangle, and a sunburst periosteal reaction. Diagnosis is confirmed with biopsy or cytology showing malignant osteoid. Thoracic radiographs are required for staging. Options A and C do not match the typical appearance of OSA, while D suggests degenerative joint disease, not neoplasia.
Question 5:
Answer: B. Amputation with adjuvant chemotherapy (carboplatin, cisplatin, or doxorubicin)
Explanation:
Amputation alone improves quality of life but median survival is only 4–6 months due to early micrometastasis. Adding systemic chemotherapy extends median survival to ~9–12 months. Palliative therapy (NSAIDs, opioids, bisphosphonates, radiation) is reserved for non-curative cases. Limb-sparing surgery can be considered, but chemotherapy remains essential for metastatic control. Cats often survive longer after amputation alone.
Answer 6:
B. Large breed dogs; metaphyseal regions “away from the elbow, toward the knee”
Explanation:
Canine osteosarcoma is most common in large and giant breeds, typically middle-aged to older dogs. Classic appendicular locations include the distal radius, proximal humerus, distal femur, and proximal tibia (“away from the elbow, toward the knee”). Cats are less commonly affected, with slower disease progression and less frequent metastasis.
Answer 7:
B. Mixed lytic-proliferative lesion with sunburst periosteal reaction
Explanation:
Osteosarcoma produces an aggressive bone lesion with cortical lysis, proliferation, Codman’s triangle, and a sunburst periosteal reaction. Diagnosis is confirmed with biopsy or cytology showing malignant osteoid. Thoracic radiographs are required for staging. Options A and C do not match the typical appearance of OSA, while D suggests degenerative joint disease, not neoplasia.
Answer 8:
B. Amputation with adjuvant chemotherapy (carboplatin, cisplatin, or doxorubicin)
Explanation:
Amputation alone improves quality of life but median survival is only 4–6 months due to early micrometastasis. Adding systemic chemotherapy extends median survival to ~9–12 months. Palliative therapy (NSAIDs, opioids, bisphosphonates, radiation) is reserved for non-curative cases. Limb-sparing surgery can be considered, but chemotherapy remains essential for metastatic control. Cats often survive longer after amputation alone.
