Squamous papilloma of the external ear in Southwest China: A large case series highlighting predominant HPV subtypes, pathologic features, and unique epidemiologic factors.

Squamous papilloma (SP) of the external ear is a rare benign neoplasm, with limited research on its associated human papillomavirus (HPV) infections and pathologic features. This study aims to provide a comprehensive analysis of the largest case series of external ear SP from Southwest China. We retrospectively collected 88 cases diagnosed with SP in the external ear canal, of which 85 (97%) were located in the external auditory canal and 3 (3%) on the auricle. We investigated the clinical, pathological, and HPV-typing characteristics using Polymerase chain reaction (PCR) and reverse dot blot (RDB) hybridization. Our series included 74 males and 14 females, with a median age of 62.5 years (range: 5-91 years). The predominant HPV type was HPV-6 (59/62, 95.2%), followed by high-risk types HPV-16 (4/62, 6.5%), HPV-52 (2/62, 3.2%), and HPV-58 (1/62, 1.6%). Histologically, all cases demonstrated typical features of SP, including koilocytes, hyperkeratosis, and basal/parabasal hyperplasia. Additionally, co-infection with multiple HPV types was observed in four cases. Notably, high-risk HPV types were detected in seven cases, all of which were completely excised with no recurrence during follow-up. This study suggests regional variations in HPV-subtype distribution and highlights potential environmental factors contributing to the prevalence of SP in Southwest China.