Osteosarcoma and Soft Tissue Sarcomas in Dogs

Musculoskeletal Neoplasia

• Musculoskeletal neoplasia is a common and problematic disease.
• Over 99% of animals die from the disease.
• There are many treatment options available.
• A good quality of life is achievable for some patients.

Learning Objectives

• The presentation aims to cover the origins of common soft tissue sarcomas.
• Factors affecting the prognosis of these types of cancers.
• The difference between canine and feline soft tissue sarcomas.
• How bone sarcomas differ.
• Major treatment options for osteosarcoma.

Classification

• Connective tissue cancers, including bone, muscle, collagen, cartilage, blood vessels, and nerves, are classified as sarcomas (-Oma).
• Epithelial tissue tumors, such as glandular, secretory, and lining tissues, are classified as carcinomas (-Oma).
• Round cell tumors, such as immune cells and melanocytes, generally end with -Oma.

Soft Tissue Sarcomas (STS)

• Spindle cell sarcoma and mesenchymal tumors are soft tissue sarcomas (STS), arising from mesenchymal origins.
• STS can arise in different body areas, including subcutaneous, alimentary, and urinary tracts.

Clinical Appearance

• Soft tissue sarcomas often present as soft, fluctuant, and mobile subcutaneous masses in dogs.
• About 15% of canine skin and subcutaneous masses are soft tissue tumors.

Palpate LNs & Haemogenous Spread

• Lymph nodes (LNs) should be palpated to check for reactive responses.
• Three-view chest radiographs are essential, as these sarcomas commonly spread via the bloodstream (haemogenous spread).
• Tumor grade (I, II, or III) correlates with the likelihood of metastasis. (I = lowest chance of spread).

Tumour Biology

• Characterized by locally aggressive and expansive growth with a malignant halo.
• Tumor cells often form a heterogenous mass.
• Extra-compartmental spread and poorly defined margins are common.
• Distant metastasis is possible, and the grade of the tumor impacts the likelihood of distant metastasis.

Enneking Resection Classification

• This classification system describes different tumour resection approaches.
• Includes terms such as pseudocapsule, reactive zone, satellite and skip metastasis.

Onyx Myxosarcoma Grade II

• This particular presentation describes radiological findings of a low-grade myxosarcoma.
• The image shows a reactive response in the lymph nodes and vascular, mesenchymal, and inflammatory responses in the myxosarcoma tissue.

Wide Removal

• Tissue removal involves a margin of normal surrounding tissue or an anatomical mesodermal barrier (e.g., fascia, cartilage, or bone).
• The wide excision extends beyond the tumor mass.

Wide - 3cm and one fascial plane - This specific comment describes a surgical approach for wide removal that considers size and fascial plane.

Treatment Algorithm

• The treatment algorithm details surgical intervention considerations based on margin assessment, histological grade and chemotherapy.
• A biopsy is the first step.
• Clean surgical margins will usually determine the histological grade.
• The strategy and approach of the surgeon will be adjusted based on the tumor grade to determine whether chemotherapy is required.

Prognosis

• Early detection and appropriate management of grade 1 and 2 tumors, typically less than 5cm in diameter, result in better prognosis.
• One-year survival rate for these tumors is 95%.
• A two-year survival rate is 91%.
• A three-year survival rate ranges from 75%.

Fibrosarcoma

• Fibrosarcomas originate from the fibroblasts.
• It can develop in skin, subcutaneous tissues, oral, and nasal cavities and have a special form in the mouth
• Histologically, it is usually low grade but biologically high-grade (meaning faster growing and invasive)
• Has 20% metastasis rate.

Myxosarcoma

• Myxosarcomas start from fibroblasts that are modified by intercellular mucin.
• The biologic behaviour follows the tumour grade.
• Grade III is noted to be multi-recurrent.

Hemangiopericytoma/PNST

• The tumor originates from pericytes or nerve sheaths.
• Similar biologic behaviour to other neurogenic sarcomas, schwannoma, and neurofibrosarcomas.
• These tumors occur throughout the body.

PNST

• PNSTs are grouped based on their relationship to the central nervous system (CNS).
• Brain/spinal cord tumors are called "root" or "plexus," and peripheral tumors are classified separately from the CNS.
• Neurological changes, such as severe neuropathic pain, are possible clinical signs.

Liposarcoma

• Liposarcomas arise from new adipose tissue (de novo) but not from existing lipoma.
• Often seen in older dogs, they are locally aggressive and metastasize.
• Common in the ventral region of the body and can be subcutaneous.
• The tumor is firmer and not as easily palpated (felt by touch) compared to a lipoma.

Infiltrative Lipoma

• Non-malignant, non-metastatic.
• Locally infiltrative growth patterns, invading surrounding local muscles, fascial planes, and other structures like joints, abdominal cavity, nerves, and bone.
• Aggressive therapies, such as radiation, may be necessary.
• Radiation aims to reduce blood supply to the tumor.

Lymphangiosarcoma

• These tumors arise from lymphatic tissue.
• They are typically regional, soft, fluctuating, and edematous masses, frequently subcutaneous.
• These tumors can metastasize and are often mistaken in biopsy for a similar type of tumor, such as hemangiosarcoma.
• Lymphangiosarcoma channels do not contain red blood cells, while hemangiosarcoma channels do.

Rhabdomyosarcoma

• Originates from striated muscle tissue and often appears in younger dogs.
• Rhabdomyosarcoma is highly invasive.
• Metastasis is a significant concern, often occurring in lungs, kidneys, spleen, and adrenal glands.
• A particular type, botryoid rhabdomyosarcoma, is sometimes found in the bladder of large young dogs.

Leiomyosarcoma

• Originates from smooth muscle tissue.
• It can spread throughout the gastrointestinal tract, spleen, retroperitoneal space, genitourinary tract, and subcutaneous tissue.
• Locally aggressive and metastasizes according to grade.
• It may cause paraneoplastic syndromes, like hypoglycemia.

Synovial Cell Sarcoma

• Originates from the tenosynovial tissue.
• Early metastasis can occur to local lymph nodes.
• Most commonly affects middle-aged dogs.
• Stiffer joints like the knee are more commonly affected than the elbow.
• Histological grade may be used in the assessment to predict the metastatic potential.
• 22% of these tumors metastisize when first diagnosed, and 41% following treatment.

Feline Sarcomas

• Feline sarcomas have three main categories: viral, non-viral/non-vaccine, and injection-site sarcomas (ISS).

Non-viral non-injection sarcoma

• Commonly affect older cats.
• Often found in head and neck regions.

Injection-site sarcomas (ISS)

• A 61% increase in incidence from 1987–1991, coinciding with a shift in rabies vaccines from modified live to killed versions.
• Adjuvants may be a contributing factor.
• This type of sarcoma is associated with a range of vaccines and vaccination products.

ISS

• FeLV vaccination
• Vaccination for other feline infectious diseases
• Non-vaccine products, such as Lufenuron and Baytril

Aluminum Adjuvant

• The adjuvant aluminum can contribute to inflammation and expression of oncogenic factors.
• Increased PDGF, PGF expression, and dysregulation of p53 are possible.
• Inflammatory granulomas can be a precursor to a sarcoma formation.

Skin adjacent to tumour vs Tumour

• Different samples from a specimen show the concentration of copper and aluminum with respect to the disease and its prevalence around the affected site. This is a microscopic scale analysis.

Vaccine reactions

• 1.8% of vaccinated cats develop post-vaccination reactions, with the lesions reaching up to 6cm in diameter.
• Reactions typically resolve within 30 to 90 days.
• Lesions that persist for longer than 6 months or that exhibit significant malignant behavior need further evaluation.

Prevention and Monitoring

• Avoid over-vaccination and use single-dose vials.
• Maintain detailed vaccine records.
• Standardize and separate vaccination injections.
• Excise or biopsy any persisting reactions that are greater than 3 months old, greater than 2cm in diameter, or that increase in size after injection
• Report to USP Veterinary Practitioners.

Natural History OSA

• Osteosarcoma (OSA) is the most common primary bone cancer in dogs and cats.
• 85% of bone tumours in dogs is due to osteosarcoma
• 80% of osteosarcoma affects long bones or appendicular skeleton.

Lameness

• Lameness can range from mild to severe and from acute to chronic.
• Evaluation of the owner's response to analgesics and whether a bone may have fractured, is critical to treatment.

Implant/Fracture Induced

• Implantation or fracture events might induce tumors.

Biopsy Options

• Cytology (fine needle aspirate, roll-prep)
• Histology (needle core (Jamshidi), Michel trephine, incisional, excisional)

Jamshidi core biopsy

• Technique for surgical tissue sampling for histology.

Tumour grade I, II, III

• Tumour grade is determined by the presence or absence of pleomorphism in cancerous cellular structures, the number of mitotic figures, and the cellularity / necrosis of the tissue.
• An assessment of grade I, II, or III affects treatment and prognosis.
• In a specific study, grade 1 and 2 tumours show only 25%, while 75% of the tumors are grade 3.

Risks of bone biopsy

• Increased lameness.
• A possible pathological fracture.
• Results sometimes are non-diagnostic.
• Possible tumour seeding.

One needle, One greyhound, & One hour later...

• This describes a complication seen in an animal subjected to a biopsy. The changes in the x-rays indicate an undesirable effect of the procedure.

You've Got a Diagnosis, Now What?...

• Treatment options for a diagnosis include palliative home care, amputation alone, palliative radiation +/− chemotherapy, amputation and chemotherapy, limb-sparing surgery (and chemotherapy), and treating a pathological fracture.

Bone Cancer

• The decision for surgical intervention, limb sparing or amputation, is heavily influenced by the extent of involvement of soft tissue, owner perspective, and costs.
• The location where the cancer originated (or if it has spread) affects the appropriate approach for treatment.
• Tumor size, location, and its growth behaviour also need to be monitored and evaluated by the surgeon for treatment.

Home-care

• NSAIDs (as needed)
• Tramadol (>5 mg/kg TID)
• Gabapentin (3-10 mg/kg TID)
• Pamidronate (1 mg/kg slow IV q4w)
• Zoledronate (0.25 mg/kg slow IV q4w).

Amputation alone

• In cases that only require amputation alone, there is reduction in bone pain, possibly with a 11% one year survival rate. It is possible to die from the effects of metastases to other organs, such as lung metastasis.

Limbspare

• The type of limb sparing will affect prognosis and outcome for the patient.

Chemotherapy

• For certain diseases, Chemotherapy can keep patients alive for a longer period.
• The median survival rate with chemotherapy for these types of diseases should be between 10-12 months.

Canine Osteosarcoma - Chemotherapy plus amputation/limb sparing

• Presentation describes the use of different chemotherapeutic drugs and their impact on survival rates, post-amputation/or amputation.

Radiation

• External beam radiation is used for various purposes.
• Intent may be curative or palliative.
• Radioactive materials are used; samarium may be systemically or regionally applied.

In summary...

• Musculoskeletal neoplasia is a significant clinical problem, where most animals eventually succumb to the disease.
• Various treatment methods are available, though outcomes are often poor.
• Quality of life and successful management are goals.

Diagnosis/Workup

• Diagnosis begins with a comprehensive clinical assessment (CBC, Chem, UA), followed by relevant radiographic images (regional radiographs).
• CT and MRI are often helpful due to the invasive nature of many of these cancers, and due to their often-difficult locations.

Staging - Distant

• A study showed that the presence of distant disease is indicative of a poor prognosis for stage 3 disease and may mean chemotherapy is ineffective .

Biopsy - Atypical location / Appearance

• Atypical locations or appearances could necessitate a biopsy.

Biopsy - 2 good reasons to try an FNA

• Thin egg-shell cortex (bone affected)
• Soft tissue extension
• FNA (fine-needle aspiration) is suggested to assess for some of the potential risks.

Biopsy Options

• Different biopsy techniques are available: cytology (fine needle aspirate, roll prep), and histology (needle core, Michel trephine, incisional/excisional).

Risks of Bone Biopsy

• Increased lameness.
• Pathological fracture.
• Non-diagnostic results.
• Tumour seeding.