MALIGNANT HISTIOCYTOSIS - HISTOLOGIC, CYTOCHEMICAL, CHROMOSOMAL, AND MOLECULAR-DATA WITH A NOSOLOGIC DISCUSSION

The histologic, chromosomal, and molecular features of malignant histi ocytosis (MH) as an entity belonging to the malignant histiocytic diso rders are reported in this article. The contributions pros vided by th e MH-derived permanent cell lines are described more specifically. The se in vitro studies have demonstrated that the MH proliferation is cha racterized by a unique chromosomal abnormality, the 5q35 usually assoc iated with a t(2;5) translocation generating a fusion gene NPM/ALK and the subsequent expression of p80 protein. In addition, these in vitro studies have shown that 5q35 proliferative cells are glass adherent, can develop an immunodependent phagocytosis, and are able to reduce NE T and produce TNF-alpha. Remarkably, they express constitutively c-fms , the receptor of the macrophage growth factor, and under phorbol dies ter stimulation, are able to modulate the expression of this receptor and its ligand as well as TNF-alpha and IL-1. An important part of the article is devoted to the nosological discussion concerning the conce ptual controversy about the T-lymphoid or histiocytic origin of the pr oliferative cells.