Coexpression of intermediate filaments in normal and neoplastic human tissues: a reappraisal

The current view that coexpression of intermediate filaments (IFs) must be considered a bizarre and unpredictable phenomenon, which seriously jeopardizes the use of their localization in diagnostic applications, is critically reviewed in light of the evidence so far acquired by investigations in vivo and in vitro. A less dogmatic approach, which considers IF expression the result of a series of interactions between cells and their microenvironment instead of a function of their histogenesis, not only justifies the complex variety of coexpressions observed in normal and neoplastic tissues but also confirms the usefulness of IF expression in diagnostic applications and offers new opportunities for investigations, with special regard to immunoelectron microscopy.