The intracellular lumen: origin, role and implications of a cytoplasmic neostructure.

Ultrastructurally, the intracellular lumen appears as a more or less spherical cavity with osmiophilic substance, bordered with microvilli and surrounded by a filamentous network. Epithelial cancer cells, both healthy cultured and hormonally stimulated in vivo, often present such structures, which probably result from a dysfunction of the Golgi apparatus and cytoskeleton. This characterizes an abortive secretory process, which may be the consequence of a great hormonal sensitivity of the cells or of a loss of differentiation criteria when they are cancerous or isolated for culture.