Human papillomavirus-associated plantar epidermoid cyst related to epidermoid metaplasia of the eccrine duct epithelium: a combined histological, immunohistochemical, DNA-DNA in situ hybridization and three-dimensional reconstruction analysis.

BACKGROUND: We recently proposed that certain palmoplantar epidermoid cysts may be related to eccrine ducts and that human papillomavirus (HPV) 60 may play a role in their pathomechanism. However, the origin of palmoplantar epidermoid cysts is still controversial.

OBJECTIVES: To examine the contribution of eccrine ducts and HPV 60 in the development of epidermoid cysts.

METHODS: Five epidermoid cysts and four ridged warts that had developed on the soles of a patient were studied histologically, immunohistochemically and by DNA-DNA in situ hybridization. Using serial sections obtained from its entire body, a three-dimensional reconstruction (3DR) analysis was performed on the smallest cyst to analyse the relationship between the epidermoid cyst, eccrine duct and the overlying epidermis.

RESULTS: Histological and DNA-DNA in situ hybridization analyses demonstrated both homogeneous intracytoplasmic inclusion bodies pathognomonic for HPV 60 infection and HPV 60 DNA sequences not only in all of the epidermoid cysts and ridged warts but also in the acrosyringeal portion of an eccrine duct, with the dermal portion of which the smallest cyst had been revealed to connect by 3DR analysis. However, immunohistochemical analyses using antibodies against human carcinoembryonic antigen (CEA), involucrin and several cytokeratins (CKs) revealed that the immunoreactivity of the cyst was not identical to that of the eccrine dermal duct but was identical to that of suprabasal layers of the epidermis.

CONCLUSIONS: It was clearly demonstrated that an HPV 60-associated epidermoid cyst with immunoreactivities for CEA, involucrin and CKs which were identical to those of the epidermis connected with the eccrine dermal duct, supporting the idea that certain palmoplantar epidermoid cysts may develop following the epidermoid metaplasia of eccrine ducts with HPV 60 infection.