Basal Cell Tetrasomy in Low-Grade Cervical Squamous Intraepithelial Lesions Infected with High-Risk Human Papillomaviruses

We have analyzed 60 low-grade cervical squamous intraepithelial lesions for low- and high-risk human papillomaviruses (HPVs) and for numerical abnormalities of chromosomes 1, 3, 11, 17, and 18 and the X chromosome. Eleven of 33 lesions infected with high-risk HPVs (HPV 16, 18, 30, 31, 33, 35, 39, 45, 51, 52, 56, 58, and 66) but none of 24 lesions infected with low-risk HPVs (HPV 6, 11, 42, 43, and 44) and none of 15 normal cervices showed basal cell tetrasomy of all six chromosomes in the HPV-infected areas. These changes were not HPV type specific and were not present in all lesions infected with the same HPV type. The presence of basal cell tetrasomy in lesions infected with high- but not low-risk HPVs suggests that induction of chromosome instability may be one mechanism underlying the biological differences between these viral types.