Veterinary Society of
Surgical Oncology

General Considerations

  • hair follicle tumors account for < 1% of skin tumors in cats and 5% of canine skin tumors
  • types: trichoepithelioma, pilomatrixoma, tricholemmoma, and trichofolliculoma

Trichoepithelioma (Hair Matrixoma)

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, GSD, and Bassett Hound
  • histologically unique form with mucinous degeneration reported in the Golden Retriever

Pilomatricoma

  • benign tumors arising from hair matrix cells and particularly pilar matrix cells
  • mean age 8.2 years
  • breed predisposition: Kerry Blue Terrier and Miniature Poodle
  • sites: shoulder and lumbrosacral region
  • slow growing, well-encapsulated, and often mineralized with 33% cystic and 33% hyperpigmented
  • malignant pilomatricoma is rare (2 cases reported) with metastasis to neurologic structures
  • treatment: surgery
  • prognosis: excellent

Tricholemmoma and Trichofolliculoma

  • rare

HAIR FOLLICLE TUMORS

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