On the ultrastructure of the gastric "borderline lesion".

The "borderline lesion" of the stomach (severe dysplasia of the protruded type) is nowadays considered to be a true precancerous lesion. Histologically, this lesion is characterized by a proliferation in the area of the glandular neck, combined with severe cellular atypia. Investigation by means of transmission electron microscopy reveals the structure of these cells to be very similar to the structure of cells of an intestinal-cell-type carcinoma of the stomach. In addition to signs for a loss of differentiation of the cells, such as the absence of rough-surfaced endoplasmatic reticulum, mucin granules, and of the polarity of the cells, remarkably frequently luminal bulges and "blebs" developed to various extents can be detected. Morphometric analysis is delineating the tendency of structural features of the borderline lesion to develop toward the gastric cancer cell. These irregularities might be expressions of the beginning of expansive growth and signs pointing to differentiation into malignant neoplasia.