An estimate is made of the frequency of occurrence of nexuses ("gap junctions") in a spectrum of human cervical epithelia, ranging from normal to malignant, since a deficiency of nexuses may be important in abnormal cell-to-cell communication in malignant tissues. The normal cervical epithelium has approximately ten nexuses per cell in the basal layer of proliferating cells and 200 nexuses per cell in the more differentiated intermediate zone. Nexuses are rare between invasive malignant epithelial cells (carcinoma cells). In many areas of cell proliferation near the edge of the tumor mass, fewer than one nexus per cell is present. However, up to four nexuses per cell can be found in some well differentiated regions of invasive carcinoma. Preinvasive malignant epithelia (severe dysplasia and carcinoma-in situ) have as few nexuses as invasive carcinoma. In abnormal but benign epithelia (squamous metaplasia and mild dysplasia), nexuses are abundant. The data indicate that a decrease in number of nexuses correlates with the severity of the morphological alteration in the dysplastic epithelium. Also the deficiency of nexuses in groups of carcinoma cells can occur many cell generations before the development of invasion of the malignant epithelium into the connective tissue. The diminution of nexuses before invasion suggests that a deficiency of nexuses may be one of the important factors in eventually permitting the development of the diffusely infiltrating type of invasion which is characteristic of highly malignant tumors such as squamous carcinomas.

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