Papillomas of the external ear canal: report of ten cases in Chinese patients with HPV in situ hybridization

Abstract

Squamous papilloma is a benign exophytic proliferation which can occur occasionally in the external ear canal. It is widely assumed that the Human Papilloma Virus (HPV) is an etiologic factor of papillomas. Available techniques for detection of HPV genomes include immunohistochemistry, Southern blot hybridization, in situ hybridization (ISH), and polymerase chain reaction. To our knowledge, HPV typing has not been reported on tissue sections of papillomas in the external ear canal. We report HPV ISH analysis in ten cases of papillomas, involving the external ear canal in Chinese patients. These papilloma excrescences were less than 1 cm in diameter, and were benign morphologically. Automated HPV ISH analysis was performed for the hybridization of DNA probes, including both low-risk and high-risk HPV subtypes. HPV ISH results revealed that seven out of ten cases were positive for low-risk HPV (6, 11), three cases demonstrated no hybridization for low-risk HPV probe, and none of the cases revealed any detection of high-risk HPV (16, 18, 31, 33, 35, 39, 51, 52, 56, 58, and 66). On follow-up after 18-29 months (average 24.5 months), eight patients were doing well, with no local recurrence after excision. Two patients were lost to follow-up. Our results confirm that benign papillomas of the external ear canal are associated with low-risk HPV infection with benign behavior and neither recurrence nor high grade dysplasia.

Fig. 1

a Photograph from Case 1 shows excrescences of papilloma of the external ear canal, usually solitary. b Photograph from the Case 4 shows the papilloma of the ear canal with projections and areas of ulceration. c Section of Case 1 shows a squamous papilloma with a central fibrovascular core and covered by keratinizing squamous epithelium. d Higher magnification of Case 8 shows HPV infected squamous cells with cytoplasmic clearing and nuclear changes. Basal layers of squamous epithelium show cellular atypia. No significant dysplasia is present. e Papilloma of the external ear canal shows numerous squamous cells with viral changes, with positive dense dark nuclei stain for HPV 6/11 low-risk types by ISH (Case 2). f Papilloma of the external ear canal shows superficial infected squamous papilloma cells positive for HPV 6/11, low-risk types. Cytoplasmic clearing is present, highlighted in dense dark nuclei (Case 3)