Verrucous cysts: histopathologic characterization and molecular detection of human papillomavirus-specific DNA.

Verrucous cyst is an uncommon newly described benign epithelial cyst which may be associated with human papillomavirus infection. The purpose of this project was to study the clinicopathological features of verrucous cysts and to demonstrate human papillomavirus (HPV) by polymerase chain reaction (PCR) in these lesions. We have analyzed 5 examples of verrucous cysts: the age range of the patients was between 37-82 years and the most common locations were face and extremities. Clinically the lesions were interpreted as cyst (2), dermatofibroma (2) and basal-cell carcinoma (1). Histopathologic examination of the biopsy specimens showed in all cases an intradermal infundibular cyst lined by a papillated and/or digitated epithelium with focal prominent hypergranulosis and irregular keratohyalin granules. Furthermore, numerous whorls of keratinocytes (so-called squamous eddies) were present within the squamous areas of the hyperplastic epithelium of the cyst, morphologically reminiscent of inverted follicular keratosis. Architectural and cytological features of malignancy were not present. Sections of paraffin-embedded tissue of the 5 verrucous cysts and of 5 "conventional" follicular cysts, infundibular type, were investigated for the presence of HPV DNA sequences by PCR using consensus primers. In all 5 cases of verrucous cysts, HPV-specific DNA sequences were detected, whereas all follicular cysts, infundibular type, were negative. These results support the concept that verrucous cysts can be added to the large spectrum of HPV-induced cutaneous neoplasms. Further studies are needed to identify the specified HPV-type in these distinctive benign cystic proliferations.