Detection of human papillomavirus infection in trichilemmomas and verrucae using in situ hybridization

It is hypothesized that trichilemmomas are 'burned out' verrucae. By performing in situ hybridization using HPV type-specific probes, we explored this concept.

Verrucae vulgaris and plantaris were positive controls, and inverted follicular keratoses (IFKs) were negative controls. Additionally, all lesions were tested for HPV genital types (low and high risk).

We analyzed 9 trichilemmomas, 20 verrucae vulgaris, 8 verrucae plana, 3 verrucae plantaris and 6 IFKs. All trichilemmomas were negative for HPV types 1, 2 and genital types. Conversely, 9/20 verrucae vulgaris, 2 verrucae plantaris, and 1 verruca plana were positive for HPV type 2. Among HPV-2 positive lesions, 2/2 verrucae plantaris and 1 verruca vulgaris (chin) were strongly positive for genital-type HPV. One verruca plana (shin) was positive for genital-type HPV only. All 6 IFKs were HPV negative.

Using HPV type 1 and 2-specific probes and mixed genital-type probes, we were unable to detect HPV in trichilemmomas. This suggests that HPV-1, HPV-2 and low and high risk genital-type HPVs are not involved in the histogenesis of trichilemmoma. We also showed that genital HPV types could be present in non-genital verrucae.