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Benign, Non-Virus Associated Lesions
Benign, Non-Virus Associated Lesions
• Epidermal Hamartomas (Nevi): Rare proliferations in dogs, possibly heritable in Cocker Spaniels; appear as pigmented, hyperkeratotic papules.
• Epidermal Hamartomas (Nevi): Rare proliferations in dogs, possibly heritable in Cocker Spaniels; appear as pigmented, hyperkeratotic papules.
◦ Treatment: Excision or oral retinoids (isotretinoin/etretinate) for large lesions.
◦ Treatment: Excision or oral retinoids (isotretinoin/etretinate) for large lesions.
• Congenital Papillomas (Foals): Developmental defect (not viral); cauliflower-like appearance; Thoroughbreds predisposed.
• Congenital Papillomas (Foals): Developmental defect (not viral); cauliflower-like appearance; Thoroughbreds predisposed.
• Canine Warty Dyskeratomas: Rare, benign neoplasms with umbilicated centers; excision is curative.
• Canine Warty Dyskeratomas: Rare, benign neoplasms with umbilicated centers; excision is curative.
Basal Cell Neoplasms
Basal Cell Neoplasms
• Basal Cell Tumors (Benign):
• Basal Cell Tumors (Benign):
◦ Common Hosts: Cats (Longhair, Himalayan, Persian) and dogs (Wirehaired Pointing Griffon, Kerry Blue Terrier).
◦ Common Hosts: Cats (Longhair, Himalayan, Persian) and dogs (Wirehaired Pointing Griffon, Kerry Blue Terrier).
◦ Appearance: Solitary, encapsulated, often hairless or ulcerated nodules; in cats, they are often pigmented.
◦ Appearance: Solitary, encapsulated, often hairless or ulcerated nodules; in cats, they are often pigmented.
• Basal Cell Carcinomas (Malignant):
• Basal Cell Carcinomas (Malignant):
◦ Characteristics: Locally invasive but rarely metastasize; senior cats and dogs most affected.
◦ Characteristics: Locally invasive but rarely metastasize; senior cats and dogs most affected.
◦ Dogs: Often called basosquamous cell carcinomas; Saint Bernards and Scottish Terriers are predisposed.
◦ Dogs: Often called basosquamous cell carcinomas; Saint Bernards and Scottish Terriers are predisposed.
Squamous Cell Carcinomas (SCC):
Squamous Cell Carcinomas (SCC):
• Predisposing Factors: Prolonged solar exposure (white-haired/minimally pigmented skin), cigarette smoke (cats), and occasionally viruses.
• Predisposing Factors: Prolonged solar exposure (white-haired/minimally pigmented skin), cigarette smoke (cats), and occasionally viruses.
• Species-Specific Patterns:
• Species-Specific Patterns:
◦ Dogs: Two forms—Cutaneous (head, abdomen) and Subungual (nailbed); Subungual forms can invade bone and metastasize (13%).
◦ Dogs: Two forms—Cutaneous (head, abdomen) and Subungual (nailbed); Subungual forms can invade bone and metastasize (13%).
◦ Cats: Most common on pinnae, eyelids, nose, or lips; Feline Bowen Disease is a multicentric in situ form associated with papilloma virus and immunosuppression.
◦ Cats: Most common on pinnae, eyelids, nose, or lips; Feline Bowen Disease is a multicentric in situ form associated with papilloma virus and immunosuppression.
◦ Horses: Most common malignant skin neoplasm; affects non-pigmented areas (periorbital, genitalia).
◦ Horses: Most common malignant skin neoplasm; affects non-pigmented areas (periorbital, genitalia).
◦ Cattle: Often periocular or vulvar; "horn core" SCC common in older bulls in India.
◦ Cattle: Often periocular or vulvar; "horn core" SCC common in older bulls in India.
◦ Sheep: Merinos predisposed; solar injury heightened by photosensitizing plants.
◦ Sheep: Merinos predisposed; solar injury heightened by photosensitizing plants.
• Treatments: Surgical excision (2 cm margins recommended), nosectomy, amputation (for digits), radiation, and chemotherapy (carboplatin, or 5-fluorouracil for dogs only).
• Treatments: Surgical excision (2 cm margins recommended), nosectomy, amputation (for digits), radiation, and chemotherapy (carboplatin, or 5-fluorouracil for dogs only).
Hair Follicle Lesions:
Hair Follicle Lesions:
• Keratinized Cutaneous Cysts:
• Keratinized Cutaneous Cysts:
◦ Types: Infundibular (most common), Isthmus catagen, Matrix, Hybrid, and Dermoid Cysts (congenital, contains hair shafts).
◦ Types: Infundibular (most common), Isthmus catagen, Matrix, Hybrid, and Dermoid Cysts (congenital, contains hair shafts).
◦ Keratomas: Found in the hoof wall of horses/cloven-hoofed animals; may cause lameness.
◦ Keratomas: Found in the hoof wall of horses/cloven-hoofed animals; may cause lameness.
• Hair Follicle Tumors:
• Hair Follicle Tumors:
◦ Trichoepitheliomas: Benign or malignant cystic neoplasms; Basset Hounds and Irish Setters predisposed.
◦ Trichoepitheliomas: Benign or malignant cystic neoplasms; Basset Hounds and Irish Setters predisposed.
◦ Pilomatricomas: Hair matrix tumors; usually benign but Malignant Pilomatricomas are aggressive and metastasize to lungs.
◦ Pilomatricomas: Hair matrix tumors; usually benign but Malignant Pilomatricomas are aggressive and metastasize to lungs.
◦ Others: Trichilemmomas (benign, Poodles), Trichofolliculomas, and Dilated Pores of Winer (senior cats).
◦ Others: Trichilemmomas (benign, Poodles), Trichofolliculomas, and Dilated Pores of Winer (senior cats).
Glandular Tumors:
Glandular Tumors:
• Apocrine Gland Tumors:
• Apocrine Gland Tumors:
◦ Benign: Adenomas; common in Great Pyrenees, Chow Chows, and Alaskan Malamutes.
◦ Benign: Adenomas; common in Great Pyrenees, Chow Chows, and Alaskan Malamutes.
◦ Malignant: Adenocarcinomas; locally invasive and frequently metastasize to draining lymph nodes.
◦ Malignant: Adenocarcinomas; locally invasive and frequently metastasize to draining lymph nodes.
◦ Anal Sac Origin: Aggressive; often causes hypercalcemia (PTHrP production); 90% metastasize to sublumbar lymph nodes.
◦ Anal Sac Origin: Aggressive; often causes hypercalcemia (PTHrP production); 90% metastasize to sublumbar lymph nodes.
• Sebaceous Gland Tumors:
• Sebaceous Gland Tumors:
◦ Benign: Hyperplasias (senile change), Adenomas (very common in older dogs/cats), and Epitheliomas.
◦ Benign: Hyperplasias (senile change), Adenomas (very common in older dogs/cats), and Epitheliomas.
◦ Malignant: Adenocarcinomas; rare but locally infiltrative.
◦ Malignant: Adenocarcinomas; rare but locally infiltrative.
• Hepatoid (Perianal) Gland Tumors:
• Hepatoid (Perianal) Gland Tumors:
◦ Driven by androgens; 95% of benign adenomas in males respond to castration.
◦ Driven by androgens; 95% of benign adenomas in males respond to castration.
◦ Adenocarcinomas: Uncommon; not responsive to castration; guarded prognosis.
◦ Adenocarcinomas: Uncommon; not responsive to castration; guarded prognosis.
Viral Papillomas (Warts):
Viral Papillomas (Warts):
• Transmission: Species-specific DNA viruses; transmitted via direct contact, fomites, or insects.
• Transmission: Species-specific DNA viruses; transmitted via direct contact, fomites, or insects.
• Clinical Presentations (Dogs):
• Clinical Presentations (Dogs):
◦ Mucous membrane papillomatosis (young dogs, oral cavity).
◦ Mucous membrane papillomatosis (young dogs, oral cavity).
◦ Cutaneous papillomas (older dogs, often solitary).
◦ Cutaneous papillomas (older dogs, often solitary).
◦ Cutaneous inverted papillomas (ventral abdomen).
◦ Cutaneous inverted papillomas (ventral abdomen).
• Management: Usually self-limiting and regress spontaneously. Cattle may be vaccinated with autogenous vaccines. Topical imiquimod or azithromycin may speed regression.
• Management: Usually self-limiting and regress spontaneously. Cattle may be vaccinated with autogenous vaccines. Topical imiquimod or azithromycin may speed regression.
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