Keratoacanthoma Flashcards
Infundibular Keratinizing Acanthoma (Keratoacanthoma, infundibular cornifying epitheliomas)
Uncommon, benign, originate from hair follicle. Hereditary basis, NOT secondary to papillomavirus.
5 years or younger, male > female. Norwegian elkhound and Keeshond higher incidence, generalized and diffuse infundibular keratinizing acanthoma complex affecting entire body, less commonly GSD and Old English sheepdogs. Solitary infundibular keratinizing acanthomas reported are collies, Lhasa apsos, and Yorkies.
Back, neck, thorax, and limbs, lesions firm to fluctuate, well-circumscribed dermal or subcutaneous masses varying from 0.5-4cm diameter with a pore opening ranging from less than 1mm to several mm in diameter. Opening has hard keratinized plug varying from small and inconspicuous to large and hornlike. Superficial lesions with large keratinous plugs easily mistaken for cutaneous horns. Can be entirely dermal or SQ, some do not communicate with the surface of the skin, and can mimic cysts.
Not invasive and do not disseminate but dogs with generalized forms comprising >50 lesions may have significant morbidity secondary to local and recurrent disease as well as additional new lesions.
Keratoacanthoma (infundibular keratinizing acanthomas) Dx and Tx
DDx: papillomas, trichofolliculomas, cutaneous horns, SCC, and cysts
Histopath: keratin-filled crypt in the dermis that opens to the skin surface, wall composed of thick, complex, folded layer or well-differentiated stratified squamous epithelium with columns of squamous cells projecting peripherally from the basal surface of the wall and forming small epithelial nests, major Histopathological differential is inverted papilloma, also well-differentiated SCC, IHC characterization of Ki-67 and AgNOR distinguish SCC and IKA.
Tx: surgical excision, cryotherapy, electro therapy, and observation without Tx. Chemo with cyclophosphamide and prednisone and immunotherapy with autologous vaccine or levamisole is ineffective and NOT recommended. Oral retinoids (isotretinoin or etretinate) has been effective for tx of multiple infundibular keratinizing acanathomas in some dogs. Retinoids, good response after 3-4 months of therapy and continued intermittently for life.
Some infundibular keratinizing acanthomas may regress spontaneously.
