False-positive polymerase chain reaction results for human papillomavirus in lichen planus: Potential laboratory pitfalls of this procedure

Background: The polymerase chain reaction (PCR) is a common tool in laboratory evaluation of tissue samples. It has been particularly useful in testing for nucleic acids of infectious organisms implicated in the pathogenesis of cutaneous diseases. Objective: Our purpose was to evaluate archival biopsy material (paraffin-embedded) of lichen planus for human papillomavirus (HPV) DNA with PCR and in situ hybridization (ISH). Methods: Tissue sections were obtained from 13 specimens of lichen planus and 10 control tissues. Standard methods for PCR and ISH were used to evaluate the presence of HPV DNA. Results: Initial PCR results demonstrated HPV DNA in 11 of 13 specimens and in none of the control tissue. However, testing for specific HPV types revealed nucleic acid contamination. ISH was negative in all specimens. Conclusion: Accurate evaluation of tissue with PCR is difficult because of the procedure's profound sensitivity. Positive results reported in the literature should be viewed with caution. Potential causes for false-positive and false-negative results should be considered.