Desmosomes and gap junctions in precarcinomatous and carcinomatous conditions of squamous epithelia. An electron microscopic and morphometrical study.

By means of morphometrical techniques we have studied the distribution of gap junctions and desmosomes in uterine epithelial cells during normal, preneoplastic and neoplastic conditions, and in skin and oral cavity during normal and neoplastic conditions. The percentage of cell surface occupied by gap junctions as well as the surface to volume ratio of these structures decreases progressively from normal to metaplastic and moderately dysplastic cervical epithelium and is practically null in more severe conditions. The percentage of cell surface occupied by desmosomes decreased significantly from normal to metaplastic epithelium; the decrease is less sharp from metaplastic epithelium to dysplastic epithelium and carcinoma in situ; it then becomes again abrupt from carcinoma in situ to invasive carcinoma. In skin and oral cavity, there is no significant change between the percentage of cell surface occupied by gap junctions as well as the surface to volume ratio of these structures in normal epithelium and basal cell carcinoma. There is a significant change between normal epithelium and squamous cell carcinoma as well as between basal cell carcinoma and squamous cell carcinoma. The percentage of cell surface occupied by desmosomes and the surface to volume ratio of desmosomes decreases significantly between normal epithelium and basal or squamous cell carcinomas as well as between basal and squamous cell carcinomas. It is probable that a lack of chemical and electronic coupling as well as a lack of mechanical adhesion play a role in determining the invasive behavior of malignant cells.