The histochemical features of the Michaelis-Gutmann body and a consideration of the pathophysiological mechanisms of its formation.

The reactions to a number of histochemical stains by Michaelis-Gutmann (MG) bodies in 13 cases of malakoplakia are described. All MG bodies contained calcium and phosphate. Iron was present in six cases. Special stains failed to reveal the presence of micro-organisms. In six cases the MG bodies contained either lecithin or sphingomyelin and in three both phospholipids were present. There was no evidence of phospholipid of bacterial cell membrane derivation. Carbohydrate staining reactions suggested the presence of a neutral polysaccharide and an acidic non-sulphated polysaccharide (such as a sialoglycan). No histochemical evidence could be adduced to implicate bacterial cell membranes in the structure of the organic matrix of the MG body. The implications of these findings in the light of the association between clinical bacterial infection and malakoplakia are discussed.