Infundibular keratinizing acanthoma

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Characteristic appearance of a digital keratoacanthoma in a dog[1]

Infundibular keratinizing acanthoma (intracutaneous cornifying epithelioma) are a rare epithelial benign keratin-containing neoplasia of hair follicles.

These skin tumors are characterized by peripheral proliferation of basaloid epithelial cells with differentiation to squamous epithelium resembling the normal follicular infundibulum/isthmus. The term of keratoacanthoma should be reserved for those tumors of subungual origin (nail-bed).

These tumors are thought to be similar histologically to squamous cell carcinoma[2].

A typical infundibular keratinizing acanthoma consists of a well-circumscribed keratin-filled crypt in the dermis and subcutis that opens to the skin surface. Most of these tumors occur on the trunk, head, eyes[3] and digits[4][5].

A breed predisposition has been reported in the Norwegian Elkhound[6], Tibetan Terrier, Kerry Blue Terrier, Briard, Bedlington Terrier, Pekingese, Collie, Yorkshire Terrier and German Shepherd[7].

Diagnosis is based on histological examination of biopsied skin, which shows characteristic keratin filled tumor lined by large squamous cells with a pale eosinophilic cytoplasm, surrounded by a compressed dermal collagenous stroma. Some may show chondroid or osseous metaplasia.

A differential diagnosis would include sebaceous adenoma, chronic solar dermatitis, basal cell carcinoma, papilloma, hepatoid gland carcinoma, mast cell tumor and squamous cell carcinoma[8].

Simple surgical excision is curative in most cases, except where additional growths develop. In these cases, multiple cryosurgery may be required with use of oral retinoids such as etretinate.


  1. Pets Canada
  2. Della Salda L et al (2002) Cell proliferation patterns in canine infundibular keratinizing acanthoma and well differentiated squamous cell carcinoma of the skin. Eur J Histochem 46(2):165-172
  3. Howell RM & Alexander VG (1971) Keratoacanthoma on the eyelid of a beagle dog. Vet Med Small Anim Clin 66(10):1022-1023
  4. Stannard AA & Pulley LT (1973) Intracutaneous cornifying epithelioma (keratoacanthoma) in the dog: a retrospective study of 25 cases. J Am Vet Med Assoc 167(5):385-388
  5. Wobeser BK et al (2007) Agreement among surgical pathologists evaluating routine histologic sections of digits amputated from cats and dogs. J Vet Diagn Invest 19(4):439-443
  6. Rudolph R et al (1977) Intracutaneous cornifying epithelioma ("keratoacanthoma") of dogs and keratoacanthoma of man. Cornell Vet 67(2):254-264
  7. University of Pennsylvania
  8. Weiss E, Frese K (1974) Tumours of the skin. Bull World Health Organ 50(1-2):79-100