Embedded Files
Overview, Etiology & General Principles:
Overview, Etiology & General Principles:
• 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:
◦ Environmental: Chemical carcinogens and ionizing radiation.
◦ Environmental: Chemical carcinogens and ionizing radiation.
◦ Biological: Genetic predisposition (breed-specific), hormones, and viruses.
◦ Biological: Genetic predisposition (breed-specific), hormones, and viruses.
• 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: Localized, encapsulated, and non-infiltrative.
◦ Benign: Localized, encapsulated, and non-infiltrative.
◦ Intermediate: Locally infiltrative but non-metastatic.
◦ Intermediate: Locally infiltrative but non-metastatic.
◦ Malignant: Infiltrative with metastatic potential.
◦ Malignant: Infiltrative with metastatic potential.
• Diagnosis: Cytology (FNA) is used for screening, while Histopathology is required for definitive diagnosis and grading.
• Diagnosis: Cytology (FNA) is used for screening, while Histopathology is required for definitive diagnosis and grading.
Lymphocytic Tumors
Lymphocytic Tumors
• Extramedullary Plasmacytomas:
• Extramedullary Plasmacytomas:
◦ Hosts: Common in mature dogs (Cocker Spaniels, Poodles); rare in cats.
◦ Hosts: Common in mature dogs (Cocker Spaniels, Poodles); rare in cats.
◦ Appearance: Small, often pedunculated nodules on the head, ears, and oral cavity.
◦ Appearance: Small, often pedunculated nodules on the head, ears, and oral cavity.
◦ Treatment: Conservative surgical excision; radiation for multiple/recurrent tumors.
◦ Treatment: Conservative surgical excision; radiation for multiple/recurrent tumors.
• Cutaneous Lymphosarcoma:
• Cutaneous Lymphosarcoma:
◦ Epitheliotropic (ECL/Mycosis Fungoides): T-cell origin; progresses from patch to plaque to tumor.
◦ Epitheliotropic (ECL/Mycosis Fungoides): T-cell origin; progresses from patch to plaque to tumor.
▪ Clinical Signs: Erythematous patches and alopecia due to follicular infiltration.
▪ Clinical Signs: Erythematous patches and alopecia due to follicular infiltration.
▪ Sézary Syndrome: ECL occurring concurrently with leukemia.
▪ Sézary Syndrome: ECL occurring concurrently with leukemia.
◦ Nonepitheliotropic (NECL): More aggressive and common in the trunk; systemic involvement occurs early.
◦ Nonepitheliotropic (NECL): More aggressive and common in the trunk; systemic involvement occurs early.
◦ Species Variations:
◦ Species Variations:
▪ Horses: Can be lymphohistiocytic (slow) or monomorphic (rapid/fatal).
▪ Horses: Can be lymphohistiocytic (slow) or monomorphic (rapid/fatal).
▪ Cattle: "Sporadic bovine leukosis" in young animals; typically non-transmissible.
▪ Cattle: "Sporadic bovine leukosis" in young animals; typically non-transmissible.
Cutaneous Mast Cell Tumors (MCT)
Cutaneous Mast Cell Tumors (MCT)
• Dogs: The most common malignant skin tumor (16–19%).
• Dogs: The most common malignant skin tumor (16–19%).
◦ Biological Behavior: Highly variable; can cause gastroduodenal ulcers due to histamine release.
◦ Biological Behavior: Highly variable; can cause gastroduodenal ulcers due to histamine release.
◦ Grading: Determined via histopathology (Patnaik or Bostock systems); high-grade tumors have a survival time of ~4 months vs. >2 years for low-grade.
◦ Grading: Determined via histopathology (Patnaik or Bostock systems); high-grade tumors have a survival time of ~4 months vs. >2 years for low-grade.
◦ Treatment: Wide surgical excision (3 cm margins); chemotherapy (Vinblastine, Lomustine); and Tyrosine-kinase inhibitors (Masitinib, Toceranib) for difficult cases.
◦ Treatment: Wide surgical excision (3 cm margins); chemotherapy (Vinblastine, Lomustine); and Tyrosine-kinase inhibitors (Masitinib, Toceranib) for difficult cases.
• Cats: Second most common skin tumor.
• Cats: Second most common skin tumor.
◦ Mast Cell Type: Usually benign, solitary nodules on the head and neck.
◦ Mast Cell Type: Usually benign, solitary nodules on the head and neck.
◦ Histiocytic Type: Occurs in young Siamese (<4 years); may regress spontaneously.
◦ Histiocytic Type: Occurs in young Siamese (<4 years); may regress spontaneously.
• Horses: Generally benign solitary masses on the head or legs; can undergo dystrophic mineralization (gritty texture).
• Horses: Generally benign solitary masses on the head or legs; can undergo dystrophic mineralization (gritty texture).
Tumors with Histiocytic Differentiation
Tumors with Histiocytic Differentiation
• Cutaneous Histiocytomas:
• Cutaneous Histiocytomas:
◦ Known as "button tumors"; common in dogs <3.5 years old.
◦ Known as "button tumors"; common in dogs <3.5 years old.
◦ Usually solitary, pink, and alopecic; most resolve spontaneously within 2–3 months.
◦ Usually solitary, pink, and alopecic; most resolve spontaneously within 2–3 months.
• Cutaneous Histiocytosis: Rare; plaques and nodules that wax and wane; common in Chinese Shar-Pei.
• Cutaneous Histiocytosis: Rare; plaques and nodules that wax and wane; common in Chinese Shar-Pei.
• Systemic & Malignant Histiocytosis:
• Systemic & Malignant Histiocytosis:
◦ Primarily affects Bernese Mountain Dogs.
◦ Primarily affects Bernese Mountain Dogs.
◦ Systemic: Episodic, progressive, and eventually fatal; affects skin, nodes, and bone marrow.
◦ Systemic: Episodic, progressive, and eventually fatal; affects skin, nodes, and bone marrow.
◦ Malignant: Highly aggressive; spares the skin but effaces the lungs, liver, and lymph nodes; usually fatal within 6 months.
◦ Malignant: Highly aggressive; spares the skin but effaces the lungs, liver, and lymph nodes; usually fatal within 6 months.
Epidermal, Hair Follicle & Glandular Tumors:
Epidermal, Hair Follicle & Glandular Tumors:
• Basal Cell Neoplasms: Benign basal cell tumors (pigmented in cats) vs. malignant basal cell carcinomas.
• Basal Cell Neoplasms: Benign basal cell tumors (pigmented in cats) vs. malignant basal cell carcinomas.
• Squamous Cell Carcinoma (SCC): Solar-induced in non-pigmented skin; subungual forms in dogs can invade bone.
• Squamous Cell Carcinoma (SCC): Solar-induced in non-pigmented skin; subungual forms in dogs can invade bone.
• Hair Follicle Tumors: Trichoepitheliomas (cystic) and Pilomatricomas (malignant forms metastasize to lungs).
• Hair Follicle Tumors: Trichoepitheliomas (cystic) and Pilomatricomas (malignant forms 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; leads to hypercalcemia.
◦ Anal Sac Adenocarcinoma: Highly aggressive; leads to hypercalcemia.
◦ Hepatoid Gland Tumors: Androgen-dependent; often respond to castration in males.
◦ Hepatoid Gland Tumors: Androgen-dependent; often respond to castration in males.
Melanocytic & Metastatic Tumors:
Melanocytic & Metastatic Tumors:
• Melanocytic:
• Melanocytic:
◦ Melanocytoma: Benign (head/limbs).
◦ Melanocytoma: Benign (head/limbs).
◦ Malignant Melanoma: Highly aggressive; common at mucocutaneous junctions and oral cavity.
◦ Malignant Melanoma: Highly aggressive; common at mucocutaneous junctions and oral cavity.
◦ Equine Gray Horse Melanoma: Found in 80% of older gray horses (tail base/perineum).
◦ Equine Gray Horse Melanoma: Found in 80% of older gray horses (tail base/perineum).
• Cutaneous Metastasis:
• Cutaneous Metastasis:
◦ Feline Lung-Digit Syndrome: Primary lung adenocarcinoma metastasizing to the feet.
◦ Feline Lung-Digit Syndrome: Primary lung adenocarcinoma metastasizing to the feet.
◦ Transmissible Venereal Tumor (TVT): Can be inoculated into haired skin via injury.
◦ Transmissible Venereal Tumor (TVT): Can be inoculated into haired skin via injury.
• Prognosis: Generally poor for metastatic disease, as it indicates systemic spread.
• Prognosis: Generally poor for metastatic disease, as it indicates systemic spread.
Page updated
Google Sites
Report abuse