General Considerations

•trichoepithelioma accounts for 80% of hair follicle tumors (and up to 2%-3% of all feline skin tumors)

•benign tumor derived from primitive hair matrix cells that show differentiation to either mature or incompletely developed hair follicles

•17.5% have histologic features of malignancy

•however, biologic behaviour is usually benign with local tumor recurrence and metastasis rare

•site: dorsal lumbar and lateral thoracic region

•gross appearance is similar to basal cell carcinoma but some are cystic and contain keratin

•intradermal mass with overlying epidermis atrophic, hairless and often ulcerated secondary to trauma

•treatment: surgery

•prognosis: excellent

Feline Trichoepithelioma

•breed predisposition: Siamese

•in cats, trichoepithelioma is well-circumscribed, > 5 cm in diameter and usually occur over dorsal lumbar area although others report small, slow-growing tumors with a predilection for the head and back

Canine Trichoepithelioma

•mean age 9.3 years

•breed predisposition: Golden Retriever, German Shepherd Dog, and Bassett Hound

•histologically unique form with mucinous degeneration reported in the Golden Retriever