In Situ Hybridization Signal Patterns in Recurrent Laryngeal Squamous Papillomas Indicate that HPV Integration Occurs at an Early Stage

Laryngeal papillomas are benign tumors that frequently recur and can compromise airways. We investigated HPV genotype, physical status, and protein expression in juveniles versus adults. Thirty-five laryngeal papilloma specimens were obtained from ten juveniles (1–16 years) and eleven adults (24–67 years). In cases of recurrent papillomatosis (7 juveniles, 7 adults), the first and last papillomas were assayed. HPV type was determined by GP5+/6+ PCR and dot blot hybridization. In situ hybridization (ISH) was performed on 34 specimens; the data were recorded in terms of diffuse (episomal HPV) and punctate (integrated HPV) signal patterns. Immunohistochemistry for the HPV L1 capsid protein, a marker of HPV productive status, was performed on 32 samples. All samples tested HPV positive: HPV 11 in 2/10 (20.0%) juveniles and 5/11 (45.5%) adults; HPV 6 in 7/10 (70%) juveniles and 5/11 (45.5%) adults; and HPV 6/11 double infection was noted in one juvenile and one adult. ISH signals (punctate ± diffuse) were detected among 7/10 (70.0%) juveniles and 7/11 (63.6%) adults. L1 staining was detected in 1/9 (11.1%) juveniles and 6/10 (60.0%) adults (P = 0.06). These data support the idea that integration of low-risk HPV types into the cell genome is an early and common event in the etiology of juvenile and adult recurrent laryngeal papillomas. Productive HPV infections may be more common in adults; accordingly, constant laryngeal re-infection by HPV shed from a productive lesion may contribute to adult recurrent lesions, whereas the mechanism of papilloma recurrence in juveniles may be more attributable to HPV integration.