Multinucleated giant cells in myeloma kidney: an ultrastructural study.

The origin of multinucleated giant cells in myeloma kidney is not yet defined. These cells have long been thought to represent tubular epithelial cells transformed in syncytia, but, more recently, they have been considered as histiocytic cells arising from the interstitial tissue. We have studied by electron microscopy the distal tubules of kidney biopsies of 5 patients affected with myeloma kidney: our ultrastructural findings do not seem to clarify the problem. In fact, in the same patient, we have observed multinucleated giant cells probably originating from epithelial tubular cells and others, probably originating from histiocytes.