Malakoplakia with digestive tract involvement in a pig.

Malakoplakia is a rare, granulomatous, inflammatory disease that mimics malignant tumors and can affect any organ. Herein is described a case of malakoplakia in a 10-month-old slaughter pig. Diffuse, pleomorphic, round cell infiltrates, mainly histiocytes, with a tumor-like growth pattern at gross examination, infiltrated the stomach, pancreas, omentum, and mesenteric lymph nodes. The histiocytes and multinucleated giant cells had concentric, target-like inclusions known as Michaelis-Gutmann bodies. Microorganisms were not detected by the periodic acid-Schiff reaction, Ziehl-Neelsen, Gram, and Warthin-Starry staining or by electron microscopic and bacteriologic investigations. Porcine circovirus type 2 and porcine reproductive and respiratory syndrome viruses were not detected by immunohistochemistry in the sections examined.