Electron Microscopic Observations on Structures Related to the Epithelial Basement Membrane in Squamous Cell Carcinoma

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Abstract
Invasive and preinvasive carcinoma of the human oral cavity were examined with attention focused on three structures related to the electron microscopic basement membrane, i.e. half-desmo-somes, filaments traversing the lamina lucida, and aperiodic fibrils extending from the basement membrane. These structures were decreased in number or changed in structure in areas where the basement membrane is incomplete or absent. The structural findings were compared to the normal morphology and discussed in relation to the function and origin of the structures. It was found that the layered pattern of the extracellular part of the half-desmo-some, reflected in the structure of the individual filament traversing the lamina lucida, is a result of the lateral aggregation of traversing filaments in register. Observations support the view that the half-desmosomes, in addition to their function as attachment devices, participate in transport of material from the basal cell. Structural and dimensional similarities between artificial SLS-aggregates and native aperiodic fibrils suggest that the latter could be regarded as a tropocollagen aggregate. The aperiodic fibrils are the most prominent structure in the region which, under the light microscope, appears to be composed of “reticulin” fibres. The reactivity of the aperiodic fibrils with periodic acid-silver methena-mine, further supports their relation to the sub-epithelial “argentophil reticulum”. The possible epithelial origin of the structures described was discussed.