Papillomavirus-induced changes in the topography of the epidermal-dermal junction: a scanning electron microscopic study of basal lamina

Papillomavirus infects human epidermal cells and causes verruca vulgaris, which is characterized by altered epidermal growth rates and differentiation patterns. There is also a prominent induced dermal proliferative response. Ten formalin-fixed skin specimens from 10 patients, each with histologically characteristic verruca vulgaris, were excised from paraffin blocks, deparaffinized in xylene, and rehydrated in graded ethanol solutions. Hydrated specimens were incubated in 90% formic acid at 45 degrees C for 18 h. Using a dissecting microscope the epidermis was gently separated from the dermis, which then was fixed in 3% glutaraldehyde and processed for scanning electron microscopy. Scanning electron microscopy showed a well-preserved epidermal-dermal junction (EDJ) covered by basal lamina. In comparison with normal EDJ, the EDJ of verruca vulgaris showed markedly elongated dermal papillae. Some papillae were broad and thin, and others were broad and thick. Irregularly shaped and branching secondary papillae were common. Also, there were changes in the basal lamina: the normal corrugation pattern was replaced by relatively smooth undulations or coarse, vertically oriented ridges on papillae. Papillary tips were often smooth. This study shows that there were prominent alterations in the topography of the EDJ and basal lamina in verruca vulgaris. This technique should be useful in evaluating epithelial-connective tissue morphologic interactions in formalin fixed archival tissue in other diseases characterized by alterations in epidermal growth rates and differentiation patterns.