Cytologic diagnosis of extravesical malacoplakia.

Malacoplakia, a rare form of chronic granulomatous inflammation, most frequently involves the urinary tract of middle-aged women. The disease represents an unusual inflammatory response to bacteria, most commonly Escherichia coli, and probably reflects some dysfunction in the immune system of the host. We describe two cases of malacoplakia involving in one patient the vagina and in the other the perianal subcutaneous tissue and lung. In both cases, the diagnosis was made concurrently by cytology and histologic examination of tissue sections. This, in turn, led to the institution of appropriate therapy with complete resolution of the disease. In smears, the characteristic von Hansemann histiocytes are larger than alveolar macrophages. They have a reticulated granular cytoplasm that is caused by excessive accumulation of lysosomal bodies, some of which upon mineralization give rise to the pathognomonic Michaelis-Gutmann body. The latter, which is usually intracellular, can be distinguished readily from psammoma bodies and should not be confused with yeasts.