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Overview & Etiology
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.
• Tissue Origins:
• Tissue Origins:
◦ Epithelial: Epidermis and adnexa.
◦ Epithelial: Epidermis and adnexa.
◦ Mesenchymal: Fibrous connective tissue, blood vessels, adipose tissue, and undifferentiated sarcomas.
◦ Mesenchymal: Fibrous connective tissue, blood vessels, adipose tissue, and undifferentiated sarcomas.
◦ Neural: Peripheral nerves and melanocytes.
◦ Neural: Peripheral nerves and melanocytes.
• Predisposing Factors: Solar exposure, chemical carcinogens, ionizing radiation, and genetic/hormonal/viral factors.
• Predisposing Factors: Solar exposure, chemical carcinogens, ionizing radiation, and genetic/hormonal/viral factors.
Undifferentiated & Anaplastic Sarcomas
Undifferentiated & Anaplastic Sarcomas
• Nature: These are malignant mesenchymal tumors.
• Nature: These are malignant mesenchymal tumors.
• Microscopic Characteristics:
• Microscopic Characteristics:
◦ Undifferentiated Sarcomas: They are difficult to characterize microscopically because they lack distinctive features such as architectural patterns, cell products, or specific cytoplasmic/nuclear features,.
◦ Undifferentiated Sarcomas: They are difficult to characterize microscopically because they lack distinctive features such as architectural patterns, cell products, or specific cytoplasmic/nuclear features,.
◦ Anaplastic Sarcomas: These are generally undifferentiated but possess specific cellular irregularities: variations in nuclear size/shape, nuclear hyperchromasia, irregular chromatin patterns, and large numbers of abnormal mitotic figures.
◦ Anaplastic Sarcomas: These are generally undifferentiated but possess specific cellular irregularities: variations in nuclear size/shape, nuclear hyperchromasia, irregular chromatin patterns, and large numbers of abnormal mitotic figures.
• Diagnosis: Often require immunohistochemistry to detect cellular markers and determine the phenotype.
• Diagnosis: Often require immunohistochemistry to detect cellular markers and determine the phenotype.
• Prognosis: The prognosis is generally poorer for anaplastic sarcomas than for undifferentiated sarcomas.
• Prognosis: The prognosis is generally poorer for anaplastic sarcomas than for undifferentiated sarcomas.
Lymphocytic, Mast Cell & Histiocytic Tumors
Lymphocytic, Mast Cell & Histiocytic Tumors
• Mast Cell Tumors (MCT): Most common malignant skin tumor in dogs; behavior is highly variable and graded via histopathology.
• Mast Cell Tumors (MCT): Most common malignant skin tumor in dogs; behavior is highly variable and graded via histopathology.
• Lymphocytic:
• Lymphocytic:
◦ Plasmacytomas: Usually benign nodules on the head/ears of dogs.
◦ Plasmacytomas: Usually benign nodules on the head/ears of dogs.
◦ Lymphosarcoma: Can be epitheliotropic (T-cell, patch/plaque/tumor progression) or nonepitheliotropic (aggressive, systemic).
◦ Lymphosarcoma: Can be epitheliotropic (T-cell, patch/plaque/tumor progression) or nonepitheliotropic (aggressive, systemic).
• Histiocytic: Includes "button tumors" (benign, often regress) and aggressive systemic/malignant histiocytosis (common in Bernese Mountain Dogs).
• Histiocytic: Includes "button tumors" (benign, often regress) and aggressive systemic/malignant histiocytosis (common in Bernese Mountain Dogs).
Epidermal, Glandular & Hair Follicle Tumors:
Epidermal, Glandular & Hair Follicle Tumors:
• Basal Cell: Benign tumors vs. malignant carcinomas (locally invasive).
• Basal Cell: Benign tumors vs. malignant carcinomas (locally invasive).
• Squamous Cell Carcinoma (SCC): Solar-induced; subungual forms can invade bone and metastasize.
• Squamous Cell Carcinoma (SCC): Solar-induced; subungual forms can invade bone and metastasize.
• Hair Follicle: Trichoepitheliomas and Pilomatricomas (malignant forms can metastasize to lungs).
• Hair Follicle: Trichoepitheliomas and Pilomatricomas (malignant forms can metastasize to lungs).
• Glandular:
• Glandular:
◦ Anal Sac Adenocarcinoma: Highly aggressive, causes hypercalcemia.
◦ Anal Sac Adenocarcinoma: Highly aggressive, causes hypercalcemia.
◦ Hepatoid Gland Tumors: Androgen-dependent; often resolve with castration.
◦ Hepatoid Gland Tumors: Androgen-dependent; often resolve with castration.
• Viral Papillomas (Warts): Generally self-limiting and regressive.
• Viral Papillomas (Warts): Generally self-limiting and regressive.
Melanocytic & Metastatic Tumors
Melanocytic & Metastatic Tumors
• Melanocytic: Melanocytomas (benign) vs. Malignant Melanoma (highly aggressive, especially in the oral cavity or nail beds).
• Melanocytic: Melanocytomas (benign) vs. Malignant Melanoma (highly aggressive, especially in the oral cavity or nail beds).
• Cutaneous Metastasis: Rare but indicates aggressive systemic disease (e.g., Feline Lung-Digit Syndrome).
• Cutaneous Metastasis: Rare but indicates aggressive systemic disease (e.g., Feline Lung-Digit Syndrome).
Diagnosis & Evaluation
Diagnosis & Evaluation
• Cytology (FNA): Essential for initial screening and treatment planning.
• Cytology (FNA): Essential for initial screening and treatment planning.
• Histopathology: Required for definitive diagnosis, grading, and margin assessment.
• Histopathology: Required for definitive diagnosis, grading, and margin assessment.
• Phenotyping: Crucial for undifferentiated/anaplastic sarcomas via immunohistochemistry.
• Phenotyping: Crucial for undifferentiated/anaplastic sarcomas via immunohistochemistry.
Treatment & Management
Treatment & Management
• Surgical Excision:
• Surgical Excision:
◦ General: Primary treatment for most skin tumors.
◦ General: Primary treatment for most skin tumors.
◦ Wide Margins: For malignant tumors, including undifferentiated and anaplastic sarcomas, excision should be deep and wide with 3-cm margins.
◦ Wide Margins: For malignant tumors, including undifferentiated and anaplastic sarcomas, excision should be deep and wide with 3-cm margins.
◦ Importance of First Surgery: For sarcomas, the first surgery combined with immediate follow-up is the most important factor in determining the outcome.
◦ Importance of First Surgery: For sarcomas, the first surgery combined with immediate follow-up is the most important factor in determining the outcome.
• Multi-modal Therapy:
• Multi-modal Therapy:
◦ Sarcomas: Often require a combination of intraoperative and follow-up oncologic techniques.
◦ Sarcomas: Often require a combination of intraoperative and follow-up oncologic techniques.
◦ Other: Radiation, systemic/intralesional chemotherapy, and tyrosine-kinase inhibitors (for MCT).
◦ Other: Radiation, systemic/intralesional chemotherapy, and tyrosine-kinase inhibitors (for MCT).
• Follow-up: Long-term monitoring (at least 2 years) is recommended to check for local recurrence.
• Follow-up: Long-term monitoring (at least 2 years) is recommended to check for local recurrence.
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