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Equine Sarcoids is the Most Common Equid Tumor:
Equine Sarcoids is the Most Common Equid Tumor:
• Prevalence: These represent 20% of all equine neoplasms and 36% of all skin tumors in horses. They show no significant sex or age predisposition.
• Prevalence: These represent 20% of all equine neoplasms and 36% of all skin tumors in horses. They show no significant sex or age predisposition.
• Etiology: Bovine papillomavirus (BPV), specifically types 1 and 2, is the primary cause. Genetic susceptibility may also be linked to equine leukocyte antigens.
• Etiology: Bovine papillomavirus (BPV), specifically types 1 and 2, is the primary cause. Genetic susceptibility may also be linked to equine leukocyte antigens.
• Transmission: Flies (houseflies/stable flies) may act as vectors; transmission also occurs via contaminated tack or existing wounds.
• Transmission: Flies (houseflies/stable flies) may act as vectors; transmission also occurs via contaminated tack or existing wounds.
• Clinical Types (6 Recognized Entities):
• Clinical Types (6 Recognized Entities):
◦ Occult: Flat, gray, hairless, and persistent.
◦ Occult: Flat, gray, hairless, and persistent.
◦ Verrucose: Gray, scabby, or warty appearance.
◦ Verrucose: Gray, scabby, or warty appearance.
◦ Nodular: Discrete, solid nodules that may ulcerate and bleed.
◦ Nodular: Discrete, solid nodules that may ulcerate and bleed.
◦ Fibroblastic: Fleshy, pedunculated, or flat-based masses that bleed easily.
◦ Fibroblastic: Fleshy, pedunculated, or flat-based masses that bleed easily.
◦ Mixed: A combination of two or more types.
◦ Mixed: A combination of two or more types.
◦ Malevolent: Extremely rare and aggressive; spreads extensively through the skin.
◦ Malevolent: Extremely rare and aggressive; spreads extensively through the skin.
• Diagnosis: Clinically straightforward if multiple types are present, but biopsy is definitive. However, biopsy carries a risk of triggering "uncontrollable expansion" of the lesion.
• Diagnosis: Clinically straightforward if multiple types are present, but biopsy is definitive. However, biopsy carries a risk of triggering "uncontrollable expansion" of the lesion.
• Management & Treatment:
• Management & Treatment:
◦ Recurrence: High rates (15%–82%) if treated by surgery alone; excised tumors often regrow more aggressively within 6 months.
◦ Recurrence: High rates (15%–82%) if treated by surgery alone; excised tumors often regrow more aggressively within 6 months.
◦ Surgery: Recommended margins are at least 0.5–1 cm.
◦ Surgery: Recommended margins are at least 0.5–1 cm.
◦ Multimodal Therapy: Combinations of ligation, cryotherapy, laser excision, radiotherapy (interstitial brachytherapy), and chemotherapy (intratumoral cisplatin or topical imiquimod/acyclovir) are used.
◦ Multimodal Therapy: Combinations of ligation, cryotherapy, laser excision, radiotherapy (interstitial brachytherapy), and chemotherapy (intratumoral cisplatin or topical imiquimod/acyclovir) are used.
Connective Tissue & Soft Tissue Sarcomas (STS)
Connective Tissue & Soft Tissue Sarcomas (STS)
• Fibroblastic Tumors:
• Fibroblastic Tumors:
◦ Fibromas: Benign discrete nodules; common in Dobermans and Boxers.
◦ Fibromas: Benign discrete nodules; common in Dobermans and Boxers.
◦ Fibrosarcomas: Most common STS in cats; highly invasive and locally recurrent.
◦ Fibrosarcomas: Most common STS in cats; highly invasive and locally recurrent.
◦ Feline Injection Site Sarcoma (ISS): Extremely aggressive; requires 5 cm lateral margins and deep excision for successful management.
◦ Feline Injection Site Sarcoma (ISS): Extremely aggressive; requires 5 cm lateral margins and deep excision for successful management.
• Vascular Tumors:
• Vascular Tumors:
◦ Hemangiomas: Benign.
◦ Hemangiomas: Benign.
◦ Angiosarcomas (Hemangiosarcomas): Highly malignant; a solar-induced cutaneous form is common in short-haired, light-skinned dogs.
◦ Angiosarcomas (Hemangiosarcomas): Highly malignant; a solar-induced cutaneous form is common in short-haired, light-skinned dogs.
• Undifferentiated & Anaplastic Sarcomas: Malignant mesenchymal tumors that lack distinctive features and require immunohistochemistry for phenotype determination.
• Undifferentiated & Anaplastic Sarcomas: Malignant mesenchymal tumors that lack distinctive features and require immunohistochemistry for phenotype determination.
Round Cell & Histiocytic Tumors
Round Cell & Histiocytic Tumors
• Mast Cell Tumors (MCT): The most common malignant skin tumor in dogs; graded by histopathology to predict behavior and survival.
• Mast Cell Tumors (MCT): The most common malignant skin tumor in dogs; graded by histopathology to predict behavior and survival.
• Lymphocytic Tumors:
• Lymphocytic Tumors:
◦ Plasmacytomas: Generally benign nodules on the head and ears.
◦ Plasmacytomas: Generally benign nodules on the head and ears.
◦ Cutaneous Lymphosarcoma: Can be epitheliotropic (slowly progressing patches/plaques) or nonepitheliotropic (aggressive/systemic).
◦ Cutaneous Lymphosarcoma: Can be epitheliotropic (slowly progressing patches/plaques) or nonepitheliotropic (aggressive/systemic).
• Histiocytic Tumors: Includes benign "button tumors" (Histiocytomas) that often resolve spontaneously, and aggressive Systemic Histiocytosis (common in Bernese Mountain Dogs).
• Histiocytic Tumors: Includes benign "button tumors" (Histiocytomas) that often resolve spontaneously, and aggressive Systemic Histiocytosis (common in Bernese Mountain Dogs).
Epithelial, Glandular & Hair Follicle Tumors
Epithelial, Glandular & Hair Follicle Tumors
• Basal Cell Neoplasms: Range from benign pigmented nodules (common in cats) to malignant basal cell carcinomas.
• Basal Cell Neoplasms: Range from benign pigmented nodules (common in cats) to malignant basal cell carcinomas.
• Squamous Cell Carcinoma (SCC): Strongly associated with solar exposure; the subungual (nailbed) form in dogs is particularly aggressive and can invade bone.
• Squamous Cell Carcinoma (SCC): Strongly associated with solar exposure; the subungual (nailbed) form in dogs is particularly aggressive and can invade bone.
• Glandular Tumors:
• Glandular Tumors:
◦ Anal Sac Adenocarcinoma: Highly aggressive; frequently causes life-threatening hypercalcemia.
◦ Anal Sac Adenocarcinoma: Highly aggressive; frequently causes life-threatening hypercalcemia.
◦ Hepatoid Gland Adenoma: Common in intact male dogs and usually responsive to castration.
◦ Hepatoid Gland Adenoma: Common in intact male dogs and usually responsive to castration.
Melanocytic & Metastatic Tumors
Melanocytic & Metastatic Tumors
• Melanocytic:
• Melanocytic:
◦ Melanocytoma: Benign; common on the head and limbs of dogs.
◦ Melanocytoma: Benign; common on the head and limbs of dogs.
◦ Malignant Melanoma: Highly aggressive at mucocutaneous junctions (lips) and oral cavity.
◦ Malignant Melanoma: Highly aggressive at mucocutaneous junctions (lips) and oral cavity.
◦ Equine Melanoma: Affects 80% of older gray horses, typically at the tail base and perineum.
◦ Equine Melanoma: Affects 80% of older gray horses, typically at the tail base and perineum.
• Cutaneous Metastasis: Rare but serious; Feline Lung-Digit Syndrome involves primary lung cancer spreading to the toes.
• Cutaneous Metastasis: Rare but serious; Feline Lung-Digit Syndrome involves primary lung cancer spreading to the toes.
Diagnostic & Surgical Principles
Diagnostic & Surgical Principles
• Cytology (FNA): Preferred for initial screening to differentiate inflammatory from neoplastic masses.
• Cytology (FNA): Preferred for initial screening to differentiate inflammatory from neoplastic masses.
• Histopathology: The "gold standard" for definitive diagnosis, tumor grading, and evaluating surgical margins.
• Histopathology: The "gold standard" for definitive diagnosis, tumor grading, and evaluating surgical margins.
• Surgical Strategy: The first surgery is the most critical for long-term success; for most malignancies, 3 cm margins are recommended to capture infiltrative "tentacles" of the tumor.
• Surgical Strategy: The first surgery is the most critical for long-term success; for most malignancies, 3 cm margins are recommended to capture infiltrative "tentacles" of the tumor.
• Monitoring: Regular follow-up for at least 2 years is advised to detect local recurrence.
• Monitoring: Regular follow-up for at least 2 years is advised to detect local recurrence.
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