Malakoplakia of the eyelid. Clinical, histopathologic, and ultrastructural characteristics.

A 56-year-old man had a slowly growing, elevated mass excised over the right medial canthus of the right eye. Results of histopathologic examination disclosed a dermal infiltrate of histiocytes ("von Hansemann histiocytes") containing the characteristic laminated, basophilic inclusions (Michaelis-Gutmann [M-G] bodies). Results of histochemical studies showed that the M-G bodies stained positively for calcium, iron, and mucopolysaccharides. Results of electron microscopic studies showed that the histiocytes contained numerous membrane-bound lysosomal bodies of variable size and density. Some histiocytes demonstrated coccobacilli, some of which were degenerated and incorporated into large phagolysosomes. The latter provided the nidus for the deposition of inorganic elements (calcium and iron) and mucopolysaccharides to form the M-G bodies which displayed concentric calcific rings with radiating spicules of hydroxyapatite crystals. The pathogenesis of malakoplakia is discussed. The case reported herein represents the third one involving the ocular adnexa. Only ten cases of cutaneous malakoplakia have been reported previously.