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Terminology & General Etiology
Terminology & General Etiology
• Animal vs. Human Terminology:
• Animal vs. Human Terminology:
◦ Melanocytoma: Benign melanocytic proliferation in animals.
◦ Melanocytoma: Benign melanocytic proliferation in animals.
◦ Malignant Melanoma: Malignant melanocytic proliferation in animals.
◦ Malignant Melanoma: Malignant melanocytic proliferation in animals.
◦ Note: In humans, "melanoma" is always malignant.
◦ Note: In humans, "melanoma" is always malignant.
• Predisposing Factors:
• Predisposing Factors:
◦ Environmental: Chemical carcinogens and ionizing radiation.
◦ Environmental: Chemical carcinogens and ionizing radiation.
◦ Biological: Genetics (breed predispositions), hormones, and viruses.
◦ Biological: Genetics (breed predispositions), hormones, and viruses.
◦ Solar Exposure: While a major factor for human melanoma, actinic damage is seldom associated with melanocytic tumors in domestic animals.
◦ Solar Exposure: While a major factor for human melanoma, actinic damage is seldom associated with melanocytic tumors in domestic animals.
Melanocytic Tumors by Species
Melanocytic Tumors by Species
• Dogs: Most common species affected.
• Dogs: Most common species affected.
◦ Melanocytomas (Benign): More frequent than malignant forms; head and forelimbs; breeds include Schnauzers, Dobermans, and Retrievers.
◦ Melanocytomas (Benign): More frequent than malignant forms; head and forelimbs; breeds include Schnauzers, Dobermans, and Retrievers.
◦ Malignant Melanomas: Locally aggressive with high metastatic potential; common at mucocutaneous junctions (lips), oral cavity, and nail beds.
◦ Malignant Melanomas: Locally aggressive with high metastatic potential; common at mucocutaneous junctions (lips), oral cavity, and nail beds.
◦ Subungual (Nail Bed) Presentation: Swelling of the digit, loss of nail, and bone destruction; often mimics osteomyelitis.
◦ Subungual (Nail Bed) Presentation: Swelling of the digit, loss of nail, and bone destruction; often mimics osteomyelitis.
• Horses:
• Horses:
◦ Gray Horses: 80% of older Lipizzaners, Arabians, and Percherons affected. Often multiple nodules at the perineum and tail base.
◦ Gray Horses: 80% of older Lipizzaners, Arabians, and Percherons affected. Often multiple nodules at the perineum and tail base.
◦ Nongray Horses: Rare; typically young horses (<2 years) on the trunk/extremities.
◦ Nongray Horses: Rare; typically young horses (<2 years) on the trunk/extremities.
• Pigs: Often congenital in Sinclair (Hormel) miniature pigs and Durocs. Can undergo spontaneous regression.
• Pigs: Often congenital in Sinclair (Hormel) miniature pigs and Durocs. Can undergo spontaneous regression.
• Cattle & Sheep:
• Cattle & Sheep:
◦ Cattle: Infrequent; Angus predisposed; mostly benign large nodular masses.
◦ Cattle: Infrequent; Angus predisposed; mostly benign large nodular masses.
◦ Sheep: Middle-aged Suffolks/Angoras; usually malignant and metastatic.
◦ Sheep: Middle-aged Suffolks/Angoras; usually malignant and metastatic.
• Cats & Goats: Rare in both species.
• Cats & Goats: Rare in both species.
Epidermal, Glandular & Hair Follicle Tumors:
Epidermal, Glandular & Hair Follicle Tumors:
• Basal Cell Neoplasms:
• Basal Cell Neoplasms:
◦ Tumors (Benign): Hairless, often pigmented nodules in cats.
◦ Tumors (Benign): Hairless, often pigmented nodules in cats.
◦ Carcinomas (Malignant): Locally invasive; common in senior cats.
◦ Carcinomas (Malignant): Locally invasive; common in senior cats.
• Squamous Cell Carcinoma (SCC): Driven by solar injury in non-pigmented skin; aggressive subungual forms in dogs.
• Squamous Cell Carcinoma (SCC): Driven by solar injury in non-pigmented skin; aggressive subungual forms in dogs.
• Hair Follicle Tumors: Includes Trichoepitheliomas and Pilomatricomas (malignant forms metastasize to lungs).
• Hair Follicle Tumors: Includes Trichoepitheliomas and Pilomatricomas (malignant forms metastasize to lungs).
• Glandular Tumors:
• Glandular Tumors:
◦ Sebaceous/Apocrine: Benign adenomas to metastatic adenocarcinomas.
◦ Sebaceous/Apocrine: Benign adenomas to metastatic adenocarcinomas.
◦ Anal Sac Adenocarcinoma: Highly aggressive; produces PTHrP leading to hypercalcemia.
◦ Anal Sac Adenocarcinoma: Highly aggressive; produces PTHrP leading to hypercalcemia.
◦ Hepatoid Gland Tumors: Androgen-dependent in males; often resolve with castration.
◦ Hepatoid Gland Tumors: Androgen-dependent in males; often resolve with castration.
Cutaneous Metastatic Tumors
Cutaneous Metastatic Tumors
• Primary Sources: Mammary adenocarcinoma, SCC, Transitional cell carcinoma, and Pulmonary adenocarcinoma.
• Primary Sources: Mammary adenocarcinoma, SCC, Transitional cell carcinoma, and Pulmonary adenocarcinoma.
• Clinical Presentation: Usually multiple, ulcerated papulonodules.
• Clinical Presentation: Usually multiple, ulcerated papulonodules.
• Feline Lung-Digit Syndrome: Primary lung tumors metastasizing to the feet/distal extremities.
• Feline Lung-Digit Syndrome: Primary lung tumors metastasizing to the feet/distal extremities.
• Prognosis: Generally poor, indicating systemic spread of an aggressive primary tumor.
• Prognosis: Generally poor, indicating systemic spread of an aggressive primary tumor.
Diagnostics & Prognostic Indicators:
Diagnostics & Prognostic Indicators:
• Cytology (FNA): Initial screening to determine tumor type.
• Cytology (FNA): Initial screening to determine tumor type.
• Histology: Required for definitive diagnosis and margin assessment.
• Histology: Required for definitive diagnosis and margin assessment.
• Immunohistochemistry:
• Immunohistochemistry:
◦ Ki67: Markers >19.5 in canine oral melanoma predict shorter survival.
◦ Ki67: Markers >19.5 in canine oral melanoma predict shorter survival.
◦ Mitotic Index: >4 mitotic figures/10 HPF indicates poor survival.
◦ Mitotic Index: >4 mitotic figures/10 HPF indicates poor survival.
• Imaging: Radiographs are essential for "festering toes" in older dogs to differentiate melanoma from infection.
• Imaging: Radiographs are essential for "festering toes" in older dogs to differentiate melanoma from infection.
Treatment Modalities
Treatment Modalities
• Surgery: Primary choice; wide margins (3 cm) or amputation for digits.
• Surgery: Primary choice; wide margins (3 cm) or amputation for digits.
• Melanoma Vaccines: Novel xenogeneic gene therapy (tyrosinase plasmid) to shrink tumors and prevent metastasis.
• Melanoma Vaccines: Novel xenogeneic gene therapy (tyrosinase plasmid) to shrink tumors and prevent metastasis.
• Chemotherapy:
• Chemotherapy:
◦ Carboplatin: Highest response rate (28%) for measurable melanoma.
◦ Carboplatin: Highest response rate (28%) for measurable melanoma.
◦ Cisplatin/Carboplatin: Used intralesionally for equine masses.
◦ Cisplatin/Carboplatin: Used intralesionally for equine masses.
• Radiation & Multi-modal: Electrochemotherapy or radiation for non-resectable or infiltrative masses.
• Radiation & Multi-modal: Electrochemotherapy or radiation for non-resectable or infiltrative masses.
• Spontaneous Regression: Noted specifically in pigs associated with lymphocytic infiltrate.
• Spontaneous Regression: Noted specifically in pigs associated with lymphocytic infiltrate.
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