Papillomavirus DNA not detected in canine lobular orbital adenoma and normal conjunctival tissue

Canine lobular orbital adenomas are benign tumors that arise from orbital glandular tissue and extend into the orbit, conjunctiva, and third eyelid. Surgical excision is challenging and recurrence rates are high following excision alone. Enucleation and exenteration reduces the likelihood of recurrence, but is a radical therapeutic option for an otherwise visual and comfortable eye. Human papillomavirus causes 4.5% of worldwide cancers in people and has been identified in up to 23% of benign salivary gland tumors. To date, the etiology of canine lobular orbital adenomas has not been established and it is reasonable to consider canine papillomaviruses as an associative agent with benign glandular tumors in dogs. Identification of the underlying etiology of these tumors may help establish treatment or preventative measures. The purpose of this study was to evaluate conjunctival and orbital tissue of phenotypically normal dogs and tissue from canine lobular orbital adenomas for the presence of papillomavirus DNA. Thirty seven canine lobular orbital adenoma samples (36 formalin fixed paraffin embedded (FFPE) tissue samples from 33 dogs and one freshly collected sample) were evaluated via polymerase chain reaction for the presence of papillomavirus DNA. Conjunctival tissue samples, from 10 dogs with normal ocular examinations, excised immediately following euthanasia, were used as phenotypically normal controls. Three FFPE and one freshly collected tissue samples previously confirmed to be positive for papillomavirus DNA were used as positive controls. PCR products verified positive controls. Papillomavirus DNA was not detected in fresh conjunctival tissue of the phenotypically normal control dogs or in samples of fresh or FFPE canine lobular orbital adenoma tissue. An association between papillomavirus and the development of canine lobular orbital adenomas is unlikely. Further research is needed to evaluate if other viruses play a role in the pathogenesis of canine lobular orbital adenomas.