Verrucous carcinoma: a light and electron microscopic, autoradiographic, and immunofluorescence study

Verrucous carcinomas of the rectum, plantar surface of the foot, and oral cavity were studied by means of light and electron microscopy, and autoradiographic and immunofluorescent techniques. Histologic examination showed that each tumor was composed mainly of mature squamous epithelium, and each had foci of slight cellular atypia. The cells in S-phase consistently were situated near the basal layer. Immunofluorescent examination with antibasement membrane antibody showed areas of marked focal thickening and other areas where basement membrane was absent. Ultrastructural examination showed reduplicated as well as normal basal lamina. Numerous interdigitating microvilli and well developed desmosomes characterized the cells above the basal layer. A proliferative basal zone underlying a thick layer of well differentiated nonproliferating keratinocytes and reduplicated basal lamina were seen in all tumors, regardless of location. These consistent findings constitute evidence that verrucous carcinoma is a morphologic and cytokinetic entity that may occur in multiple anatomic sites.