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General Overview & Etiology:
General Overview & Etiology:
• Prevalence: Skin tumors are the most frequently diagnosed neoplasms in domestic animals.
• Prevalence: Skin tumors are the most frequently diagnosed neoplasms in domestic animals.
• Predisposing Factors:
• Predisposing Factors:
◦ Environment: Constant exposure to external carcinogens and ionizing radiation.
◦ Environment: Constant exposure to external carcinogens and ionizing radiation.
◦ Biologic: Genetic predisposition, hormonal factors, and viral infections.
◦ Biologic: Genetic predisposition, hormonal factors, and viral infections.
• Tissue Origins:
• Tissue Origins:
◦ Epithelial: Epidermis and adnexa.
◦ Epithelial: Epidermis and adnexa.
◦ Mesenchymal: Connective tissue, blood vessels, and adipose tissue.
◦ Mesenchymal: Connective tissue, blood vessels, and adipose tissue.
◦ Neural: Peripheral nerves and melanocytes.
◦ Neural: Peripheral nerves and melanocytes.
Classification of Lesions:
Classification of Lesions:
• Hamartoma (Nevus): Developmental defects (e.g., sebaceous or epidermal hamartomas).
• Hamartoma (Nevus): Developmental defects (e.g., sebaceous or epidermal hamartomas).
• Benign Neoplasms: Localized, encapsulated, and non-infiltrative.
• Benign Neoplasms: Localized, encapsulated, and non-infiltrative.
• Intermediate Malignancy: Locally infiltrative but do not metastasize.
• Intermediate Malignancy: Locally infiltrative but do not metastasize.
• Malignant Neoplasms: Infiltrative with the potential for metastasis.
• Malignant Neoplasms: Infiltrative with the potential for metastasis.
• Metastatic Tumors: The spread of a primary neoplasm from another site to the skin.
• Metastatic Tumors: The spread of a primary neoplasm from another site to the skin.
Specific Primary Tumors
Specific Primary Tumors
• Basal Cell Neoplasms:
• Basal Cell Neoplasms:
◦ Basal Cell Tumors: Usually benign, solitary, and hairless nodules.
◦ Basal Cell Tumors: Usually benign, solitary, and hairless nodules.
◦ Basal Cell Carcinomas: Malignant and locally invasive but rarely metastasize.
◦ Basal Cell Carcinomas: Malignant and locally invasive but rarely metastasize.
• Squamous Cell Carcinoma (SCC):
• Squamous Cell Carcinoma (SCC):
◦ Associated with solar exposure in white-haired or non-pigmented skin.
◦ Associated with solar exposure in white-haired or non-pigmented skin.
◦ Can be cutaneous or subungual (nailbed); subungual forms can invade bone.
◦ Can be cutaneous or subungual (nailbed); subungual forms can invade bone.
• Hair Follicle Tumors:
• Hair Follicle Tumors:
◦ Trichoepitheliomas: Benign or malignant cystic neoplasms.
◦ Trichoepitheliomas: Benign or malignant cystic neoplasms.
◦ Pilomatricomas: Matrix tumors; malignant versions are aggressive and metastasize to lungs.
◦ Pilomatricomas: Matrix tumors; malignant versions are aggressive and metastasize to lungs.
• Glandular Tumors:
• Glandular Tumors:
◦ Sebaceous/Apocrine: Range from benign adenomas to invasive adenocarcinomas.
◦ Sebaceous/Apocrine: Range from benign adenomas to invasive adenocarcinomas.
◦ Anal Sac Adenocarcinoma: Highly aggressive; often causes hypercalcemia.
◦ Anal Sac Adenocarcinoma: Highly aggressive; often causes hypercalcemia.
◦ Hepatoid Gland Tumors: Benign forms in males are often androgen-dependent (responsive to castration).
◦ Hepatoid Gland Tumors: Benign forms in males are often androgen-dependent (responsive to castration).
• Viral Papillomas (Warts): Generally self-limiting and regressive; caused by species-specific DNA viruses.
• Viral Papillomas (Warts): Generally self-limiting and regressive; caused by species-specific DNA viruses.
Cutaneous Metastatic Tumors
Cutaneous Metastatic Tumors
• Prevalence: Unusual in domestic animals; identified occasionally in dogs, less common in cats, and rare in horses, cattle, sheep, and pigs.
• Prevalence: Unusual in domestic animals; identified occasionally in dogs, less common in cats, and rare in horses, cattle, sheep, and pigs.
• Primary Tumors with High Metastatic Potential:
• Primary Tumors with High Metastatic Potential:
◦ Mammary gland adenocarcinomas.
◦ Mammary gland adenocarcinomas.
◦ Squamous cell carcinomas (SCC).
◦ Squamous cell carcinomas (SCC).
◦ Transitional cell carcinomas.
◦ Transitional cell carcinomas.
◦ Transmissible venereal tumors (TVT).
◦ Transmissible venereal tumors (TVT).
◦ Pulmonary adenocarcinomas.
◦ Pulmonary adenocarcinomas.
◦ Angiosarcomas.
◦ Angiosarcomas.
• Clinical Presentation:
• Clinical Presentation:
◦ Appearance is variable but most commonly presents as multiple, ulcerated papulonodules.
◦ Appearance is variable but most commonly presents as multiple, ulcerated papulonodules.
◦ Early Evolution: Aggregates of neoplastic cells within superficial and deep dermal vessels.
◦ Early Evolution: Aggregates of neoplastic cells within superficial and deep dermal vessels.
◦ Advanced Evolution: Extension into the dermis with effacement of skin adnexa.
◦ Advanced Evolution: Extension into the dermis with effacement of skin adnexa.
• Diagnostic Challenges: It is often difficult to identify the primary tumor based on the metastatic site because only a specific subset of cells metastasizes and they may look morphologically different from the primary mass.
• Diagnostic Challenges: It is often difficult to identify the primary tumor based on the metastatic site because only a specific subset of cells metastasizes and they may look morphologically different from the primary mass.
• Feline Lung-Digit Syndrome: A specific condition where pulmonary adenocarcinomas preferentially metastasize to the distal extremities (feet).
• Feline Lung-Digit Syndrome: A specific condition where pulmonary adenocarcinomas preferentially metastasize to the distal extremities (feet).
• Prognosis: Typically guarded to poor as cutaneous metastasis indicates an aggressive tumor.
• Prognosis: Typically guarded to poor as cutaneous metastasis indicates an aggressive tumor.
Diagnosis & Evaluation:
Diagnosis & Evaluation:
• Cytology (FNA): Useful for initial screening and treatment planning.
• Cytology (FNA): Useful for initial screening and treatment planning.
• Histopathology: Required for definitive diagnosis and determining malignancy.
• Histopathology: Required for definitive diagnosis and determining malignancy.
• Immunohistochemistry: Used to determine the specific phenotype of poorly differentiated cells.
• Immunohistochemistry: Used to determine the specific phenotype of poorly differentiated cells.
• Imaging: Radiographs are recommended if multiple carcinomas are found on a cat's feet to check for primary lung tumors.
• Imaging: Radiographs are recommended if multiple carcinomas are found on a cat's feet to check for primary lung tumors.
VI. Treatment & Management
VI. Treatment & Management
• Surgery: Primary treatment; wide margins (3 cm) are recommended for suspected malignancies.
• Surgery: Primary treatment; wide margins (3 cm) are recommended for suspected malignancies.
• Radiation & Chemotherapy: Used for round cell tumors, non-resectable masses, or as follow-up for metastatic/aggressive disease.
• Radiation & Chemotherapy: Used for round cell tumors, non-resectable masses, or as follow-up for metastatic/aggressive disease.
• Other Therapies: Cryosurgery (for benign/superficial lesions), immunotherapy, and electrochemotherapy.
• Other Therapies: Cryosurgery (for benign/superficial lesions), immunotherapy, and electrochemotherapy.
• Follow-up: Continuous monitoring for at least 2 years is recommended post-surgery.
• Follow-up: Continuous monitoring for at least 2 years is recommended post-surgery.
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