Canis ISSN: 2398-2942

Skin: cutaneous papilloma

Contributor(s): John Munday, Susan E Shaw

Introduction

  • Cutaneous papillomas in dogs can be subdivided into viral papillomas and squamous papillomas.
  • Viral papillomas are caused by canine papillomavirus type 2 while squamous papillomas are spontaneous lesions.
  • Viral papillomas are subdivided into exophytic papillomas and inverted papillomas.
  • Viral papillomas are common self-resolving lesions that typically develop on younger dogs while squamous papillomas tend to be on older dogs and do not spontaneously resolve.
  • Signs: exophytic and squamous papillomas are discrete raised lesions that appear warty.
  • Inverted papillomas appear as raised plaques that can have an umbilicated appearance.
  • Diagnosis: clinical appearance or histopathology.
  • Treatment: surgical resection if causing clinical problems.
  • Prognosis: viral papillomas spontaneous regress while squamous papillomas typically remain small.

Pathogenesis

Etiology

  • Cutaneous viral papillomas are predominantly caused by canine papillomavirus type 2. Canine papillomavirus type 6 may be an additional rare cause of these lesions.
  • Eyelid papillomas and nasal planum papillomas are more likely to be caused by canine papillomavirus type 1 (the cause of canine oral papillomas).
  • The cause of nailbed papillomas of dogs is currently unknown.
  • Squamous papillomas are not caused by papillomaviruses and are of unknown cause.

Pathophysiology

  • Viral papillomas:
    • Infection of basal cells by the papillomavirus results in viral gene expression.
    • Expression of viral genes results in rapid mitosis of cells within the suprabasilar layers of the epidermis.
    • The uncontrolled cell division within the epidermis results in marked thickening of the epidermis.
    • In an exophytic papilloma the thickened epidermis becomes folded resulting in a warty mass while the thickened epidermis forms a cup-like structure containing trapped keratin in an inverted papilloma.
    • There is little evidence that cutaneous papillomas can undergo malignant transformation.
  • Squamous papillomas:
    • Epidermal thickening is spontaneous.
    • The thickened epidermis becomes folded resulting in a papillomatous lesion.

Timecourse

  • Viral papillomas develop a few weeks after infection.
  • Resolution is expected to be complete within 6 weeks although can take up to a year in rare cases.
  • Squamous papillomas do not spontaneously resolve although generally remain small.

Epidemiology

  • Epidemiology of infection poorly understood.
  • Most papillomas develop without a history of contact with an animal with papillomas.
  • Evidence suggests dogs can have productive (shedding) infections without the presence of visible lesions.
  • Young dogs are presumably predisposed to viral papillomas as this is when they are first exposed to the papillomavirus.
  • Dogs do not develop further papillomas after resolution but may continue to shed virus at low levels.
  • Immunosuppression may delay spontaneous resolution and result in the development of larger and more extensive papillomas.
  • However, dogs with delayed resolution may have no other evidence of immunosuppression.
  • Multiple papillomas have been reported secondary to clipping prior to surgery presumably due to infection of microtraumatized skin by papillomavirus.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Rector A, Van Ranst M (2013) Animal papillomaviruses. Virology 445 (1-2), 213-223 PubMed.
  • Lange C E, Favrot C (2011) Canine papillomaviruses. Vet Clin North Am Small Anim Pract 41 (6), 1183-1195 PubMed.
  • Lange C E, Zollinger S, Tobler K et al (2011) Clinically healthy skin of dogs is a potential reservoir for canine papillomaviruses. J Clin Microbiol 49 (2), 707-709 PubMed.
  • Munday J S, French A F, MacNamara A R (2010) The development of multiple cutaneous inverted papilloma following ovariohysterectomy in a dog. NZ Vet J 58 (3), 168-171 PubMed.
  • Lange C E, Tobler K, Brandes K et al (2009) Canine inverted papillomas associated with DNA of four different papillomaviruses. Vet Dermatol 21 (3), 287-291 PubMed.
  • Campbell K L, Sundberg J P, Goldschmidt M H et al (1988) Cutaneous inverted papillomas in dogs. Vet Pathol 25 (1), 67-71 PubMed.

Other sources of information

  • Gross T L, Ihrke P J, Walder E J (2005)Skin diseases of the dog and cat: clinical and histopathologic diagnosis.2nd edn. Blackwell Science, Oxfird, UK.
  • Goldschmidt M H, Hendrick M J (2002)Tumors of the Skin and Soft Tissues.In: Meuten D J (ed).Tumors in Domestic Animals.4th edn, Iowa State Press, USA.


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