Malakoplakia of the Maxillary Sinus

: The first case of malakoplakia in the nasal cavities is reported. The patient, a 21-year-old man, presented a polypoid formation in the left maxillary sinus that was removed and studied by light and electron microscopy. The polypoid formation consisted of pseudostratified epithelium surrounding a central myxoid tissue which contained fibroblasts, histiocytes, and small inflammatory infiltrates. The most relevant features were histiocyte accumulations containing 1 to 5-microns diameter granules which displayed a concentric multilayered configuration. Ultrastructural findings revealed three types of lysosomes within the histiocyte cytoplasm: phagolysosomes, intermediate bodies, and Michaelis-Gutmann bodies. Septate junctions between lysosomes were frequent. The etiopathogenesis of this lesion is discussed.