Veterinary Tumor Diagnosis Quiz

Approach to Nodular Dermatoses/Neoplasia

• Nick Bacon is an expert in veterinary dermatology and oncology
• He is a founding fellow of ACVS (American College of Veterinary Surgeons) and a specialist in surgical oncology
• He is a clinical director at AURA Veterinary and a professor at the University of Surrey

Patient Case Example

• A dog, Buddy, has a skin tumor
• Owner was told there's a chance of melanoma based on the tumor's color
• Buddy will undergo surgery to remove the tumor
• The removed tumor will be sent to a lab for testing

Common Canine Cutaneous Neoplasms

• Data on the incidence of various tumor types in dogs are presented.
• Lipoma is the most common tumor type, followed by adenoma.
• Other frequently observed types include mast cell tumors, papillomas, histiocytomas, and various sarcomas (e.g., hemangiosarcoma, fibrosarcoma, and lymphangiosarcoma).
• Melanoma and other tumors are also listed

Feline Cutaneous Tumors

• Basal cell tumors, mast cell tumors, and fibrosarcoma are common in cats
• Squamous cell carcinoma, and sebaceous adenoma/hyperplasia are also frequently observed

History Taking for Skin Tumors

• Duration/chronicity of the condition
• Growth rate and changes in the tumor's characteristics
• Previous masses or growths at the same location
• Travel history
• Breed and age may be helpful in some cases (e.g., boxers, bulldogs, and Boston terriers)
• Young dogs are more prone to histiocytomas and papillomas

Key Parameters for Evaluating Skin Lesions

• Skin vs. subcutaneous location
• Appearance (alopecia, color changes, ulceration, bleeding, etc.)
• Size using RECIST criteria (longest dimension) and body mapping
• Importance of evaluating 3D dimensions (length, width, height)

Pre-operative Biopsy

• Fine needle aspiration to establish diagnosis
• Pincushion/capillary technique involves avoiding negative pressure; this method reduces cell distortion and works well for easily exfoliating tumors, like round cell and epithelial neoplasms
• Aspiration with negative pressure is better suited for dense tumors

Cytology

• Diff-Quik staining is adequate for most diagnoses
• However, mast cell tumors (MCTs) may stain poorly with Diff-Quik (5-10% of cases)

Diff-Quik Staining Techniques

• Fixative
• Solution I (pink)
• Solution II (blue)

Non-diagnostic Aspirates

• If no cells are seen in the aspirate, the sample is deemed non-diagnostic
• Potential causes for a non-diagnostic result include the tumor's absence or a lack of viable cells
• In any case, failure to identify cells in the aspirate is important information for further evaluation

Canine Neoplasia Incidence Rates

• Incidence rates for different tumor types in the UK, considering insured dogs, are presented (e.g., histiocytoma, lipoma, adenoma)

Primary and Secondary Criteria for Cytological Diagnosis

• High nuclear-to-cytoplasmic ratio, prominent nucleoli, anisokaryosis, and nuclear pleomorphism are primary criteria
• Criteria such as multinucleation, basophilic cytoplasm, and high mitotic index are secondary criteria

Algorithm for Cytological Evaluation

• Based on the sample type, proceed through an algorithm to distinguish between benign and malignant tumors or between other possible entities
• Epithelial, mesenchymal, and round cell types can be differentiated based on shape, cellularity, cell association, and the location of the nucleus.

Categorizing Tumors

• Tumors are categorized into epithelial (carcinoma, glandular/lining tissues), mesenchymal (sarcoma, connective tissue), and discrete cell/round cell (mast cell tumor, lymphoma, histiocytoma, plasmacytoma, melanoma) categories

Locations of Different Tumor Types

• The origin or suspected spread of different categories of tumors (epithelial, mesenchymal, and discrete cell/round cell) is described.
• Specific sites of interest include lymph nodes, lungs, liver, spleen

Reasons for Biopsy

• Obtain definitive diagnosis and histological grade
• Lesions in difficult areas for reconstruction (e.g., head, neck, tail, periocular, perineal)
• Knowledge of the specific tumor type impacts client treatment decisions.

Biopsy Techniques

• Needle core biopsy (for soft tissues)
• Tru-cut biopsy
• Incisional biopsy
• Excisional biopsy (treating the patient while acquiring information / diagnosis)

Excisional Biopsy Considerations

• Treatment is not altered by histopathology
• FNA diagnoses can be helpful in making the diagnosis
• Excisional biopsy ensures that the lesion or tumor is completely removed without compromise of the patient's treatment choices.

Excisional Biopsy Limitations

• Poor excisional biopsy can compromise definitive surgical resection
• Difficult to remove the malignant cells completely leaving them behind in the body
• Metastasis may need to be evaluated prior to surgery

Excisional Biopsy Alternatives

• Biopsys may not be optimal in all cases
• Dirty margins may require additional difficult surgeries

Differentials

• Papilloma (young dogs associated with viruses, typically resolves spontaneously), histocytoma (young dogs, solitary, resolve within weeks, conservative surgery often sufficient), mast cell tumor (up to 21% skin masses, no sex preference, increased risk with age, retrievers, boxers, Shar-pei, pugs, obese dogs more prone)

Stages and Grades

• Tumor stage and grade are important data to collect in cases of malignant tumors.

Prognostic Factors for Canine Skin Tumors

• Appearance
• Growth rate and duration (>7 months)
• Paraneoplastic signs
• Clinical stage
• Histological grade
  • Size (<5cm vs >5cm)
  • Depth of tumor (superficial vs. deep)
  • Mobility (mobile vs. fixed)
  • Grade (low vs. high)

Specific Tumor Types and Locations

• Mast cell tumors (MCTs) prevalence, preputial or inguinal are less severe, while tumors of the muzzle are more aggressive with higher metastatic potential)
• Soft tissue sarcoma and where the tumor can arise
• Soft, fluctuant, mobile, and subcutaneous skin/SQ masses (15% of canine cases)
• Categories are determined (epithelial, mesenchymal, and discrete cell/round cell) to guide prognostic evaluation and treatment choices

Squamous Cell Carcinoma (SCC)

• Less common in dogs compared to cats
• Can develop in nail beds, planum, and anus.

Basal Cell Tumors

• Usually benign
• Common in cats
• Often fluid-filled cysts
• Typically found on head, neck, or shoulders

Sebaceous Tumors

• Hyperplasia or warts
• Cured with conservative surgery
• Adenomas and carcinomas are less common

Hair Follicle Tumors (Trichoepithelioma and Pilomatricoma)

• Usually benign
• Cured with conservative surgery
• Malignancy/metastasis very rare

Melanoma

• Typically less than 2cm in diameter.
• 85% of cases are benign
• 3 mitoses per 10 high-power fields
• Muco-cutaneous and oral forms can also occur

Lipomas

• Surgery is usually indicated for lipomas in situations like rapid growth, texture changes, restricting function, bothering the dog, or bothering the owner

Ear Canal Tumors

• Older cats and dogs are susceptible to ear canal problems
• Tumors often are polyps, cysts, papillomas, or adenomas.
• Ceruminous adenocarcinoma/SCC are locally aggressive with metastasis in less than 15% of cases.
• Median survival times are presented for both dogs and cats.

Summary of Important Considerations for Skin Tumors

• Biopsy is crucial for proper diagnosis and classification
• Treatment is often more easily chosen with the complete characterization of the tumor

Thank you Note

• There is a gratitude message to the audience
• There are logos of the Veterinary Societies and institutions.