Proliferating cell nuclear antigen distribution in verrucous carcinoma of the skin

Verrucous carcinoma (VC) of the skin is a rare variety of well-differentiated squamous cell carcinoma (SCC) characterized by aggressive local growth and a low metastatic potential. These tumours are known to have histological and virological features similar to classic warts or condylomata. The aim of the present study was to map the proliferative compartment in VC (n = 7) in comparison with warts (n = 10) and typical well-differentiated SCC (n = 10). The proliferating cells were detected by immunostaining of proliferating cell nuclear antigen (PCNA) in formalin-fixed, paraffin-embedded tissue sections, using the commercially available anti-PCNA monoclonal antibody PC10. Normal epidermis served as a positive control and reference. In VC and warts, the PCNA-positive cells were principally located at the periphery of lesions, in the basal layer of the tumour islands. In some warts, however, stronger PCNA expressed was noted in the superficial layers, of the lesions corresponding to virus-infected keratinocytes (koilocytotic cells). In contrast, in SCC, PCNA-positive cells were randomly scattered throughout the tumours. Our findings suggest that, on the basis of mapping of PCNA distribution, VC resembles large warts or condylomata rather than typical SCC. Thus, VC appears to be a distinct clinical entity, intermediate between these two types of lesions, not only because of its clinical entity, intermediate between these two types of lesions, not only because of its clinical and virological features, but also with regard to its proliferative organization.