[Ultrastructure of hemidesmosomes in invasive laryngeal carcinoma (author's transl)].

The occurence, distribution, and ultrastructural morphological of hemidesmosomes in malignant epithelial cells of invasive squamous cell carcinoma of human larynx were studied by electron microscopy. In the more advanced invasive carcinomas, the hemidesmosomes were reduced in number or were absent as was the basement membrane over extensive areas of the epithelial-connective tissue junction. In other places structural alterations of the hemidesmosomes were seen as a defective attachment plaque on the cytoplasmic side of the internal leaflet of the plasmalemma including retraction or absence of the inserting tonofilaments. Other structural changes were found to involve the basement membrane and the associated subbasal fibrous elements of the epithelial-stromal junction. Hemidesmosome-containing areas of the basal plasma membrane were seen to invaginate and to appear to pinch off. It was observed that the detached hemidesmosomes rounded up with their cytoplasmic attachment plaque lying on the inner circumference of the vesicular structures. These vesicular hemidesmosomes contained components of their extracellular portion. The observations indicate that autophagocytosis of detached hemidesomosomes may lead to the reduction of epithelial-dermal adherence and may thus facilitate the invasion of the underlying stroma by invasive carcinomas of the larynx.