[Ultrastructure of tumor-stroma junction of invasive laryngeal carcinoma (author's transl)].

The tumor-stroma junction of invasive squamous cell carcinoma of the larynx was examined electron microscopically. Polymorphic cytoplasmic protrusions (blebs) with a diameter ranging from 2--4 micron to 8--10 micron were observed on the basal and lateral surfaces of the malignant keratinocytes. A system of cytoplasmic 6--8 nm microfilaments can be seen consistently at the base of the blebs. The microfilaments possibly serve as a contractile ring during the pinching-off process of the blebs from the malignant keratinocytes. The blebs were observed at various stages of development until the pinching-off process occurred. They have varying shapes, sizes, and electron density and are plasmamembrane bounded. They contain hyaline ectoplasm, ribosome particles, a fine filamentous and fine granular material as well as some lysosomes. The blebbing phenomenon is discussed in respect to the cellular locomotion of malignant keratinocytes and interpreted as a possible temporary invasion mechanism in the preliminary stages of the tumor growth.