Previously unreported "hemidesmosomal junctions" between folliculo-stellate cells and pituitary adenoma cells.

Thirty-eight non-functioning pituitary adenomas were ultrastructurally investigated with particular attention to the Folliculo-Stellate (FS) cells. A large number of FS cells were found in four cases, one of which disclosed a new type of intercellular junction between FS cells and surrounding adenoma cells. These junctions were characterized by 1) the presence of plasmalemmal attachment plaques only in FS cells, 2) the cytoplasmic filaments assembling in parallel to the attachment plaques, 3) the parallel plasma membranes being separated by the intercellular amorphous material and 4) the intercellular space of approximately 25 nm width. They were similar to hemidesmosomes, but were quite different from hemidesmosome-like intercellular specializations which have been described in the normal meninges and human meningiomas. Accordingly, we designated these new junctions as "hemidesmosomal junctions" which appeared to be one of the ultrastructural features characterizing FS cells.