LAUSR

Abstract Background: Keratoacanthoma is a common cutaneous neoplasia in humans that most often occurs on sun exposed sites and is considered a rapidly growing pseudomalignancy, resembling squamous cell carcinoma (SCC), which most likely derives from the hair follicle cells [Schwartz A.R. The keratoacanthoma. JAAD 1994;30:1-19. http://doi.org/10.1016/S0190-9622(94)70001-X]. Macroscopic changes can not differentiate the cause of the skin lesions, and histology is needed to differentiate the two tumors, although in some cases keratoacanthoma and SCC have been used interchangeably in broiler chickens and parakeets [Fallavena L.C.B., Moraes H.L.S., Salle C.T.P. et al. Diagnosis of skin lesions in condemned or downgraded broiler carcasses—a microscopic and macroscopic study. Avian Pathol. 2000;29:557-562. doi: 10.1080/03079450020016797; Hafner S., Harmon B.G., Stewart R.G., Rowland G.N. Avian keratoacanthoma (dermal squamous cell carcinoma) in broiler chicken carcasses. Vet Pathol 1993;30:265-270. https://doi.org/10.1177/030098589303000307 ; Yildirim M.Z., Bilgihan Ozturk S.E., Pekcan Z. et al. Dermal squamous cell carcinoma (avian keratoacanthoma) in parakeets. Veteriner Fakultesi Dergisi. 2010;57:267-270. DOI: 10.1501/Vetfak_0000002437 ]. Case description: Beak keratoacanthomas were diagnosed in two birds from two different households: in a 10-year-old male and in a 1-year-old male budgerigar (Melopsittacus undulatus). The main clinical finding in both birds were hyperkeratotic lesions on and around the beak caused by Knemidocoptes spp. mites and a mass formation on the side of the lesions. Both masses were solid red, ulcerated, and would bleed easily. Conclusions: Histology results revealed invasive epithelial neoplastic changes with centripetal keratin formation resembling epithelial keratoacanthomas that were formed due to the extensive epithelial damage. Both birds died from profuse hemorrhaging from the well-vascularized tumor. No keratoacanthoma formations were observed in the female cage mates. Case relevance: In the two cases described in this report keratoacanthomas developed in animals with extensive skin lesions caused by Knemidocoptes spp. infection. Further studies are warranted to confirm the association between these disorders.