Xanthogranulomatous pseudotumor of the vagina: evidence of a local response to an unusual bacterium (mucoid Escherichia coli).

Utilization of nonconventional bacterial strains and electron microscopy occasionally may aid in the recognition of unusual microorganisms which fail to be demonstrated by more conventional bacterial stains. We report an unusual case of recurrent vaginal polyps, initially thought by physical examination to represent a malignant neoplasm and histologically to represent a granular cell tumor. The lesions were comprised microscopically of sheets of large, polygonal, histiocytic-like cells with abundant eosinophilic granular cytoplasm. With the Dieterle silver stain, the cytoplasm of these cells contained large numbers of intracellular rod-shaped bacilliform bodies thought to be microorganisms. These organisms stained not at all or very poorly with more conventional bacterial stains, such as Gram and Giemsa stains. Electron microscopy was employed to confirm the presence of intra- and extracellular bacilliform bodies and the absence of large numbers of cytosegresomes, the latter characteristically seen in typical granular cell tumors. Cultures of tissue from the biopsy documented a pure strain of a mucoid form of Escherichia coli. We were unable to identify any prior report describing a similar recurrent inflammatory vaginal lesion in which mucoid E. coli was demonstrated. We discuss possible pathogenesis of this case, and relate it to morphologically similar diseases, such as Whipple's disease and malakoplakia, in which there appears to be defective clearance of bacteria from a variety of tissues.