Malacoplakia of the Colon and Rectum: Report of Two Cases and Review of the Literature

Abstract

Malacoplakia of the colon and rectum is uncommon with only 30 cases having been reported in the literature. This paper documents two additional cases involving the colon and rectum. The first patient had extensive disease involving virtually the entire rectum and colon and portions of the terminal ileum. The clinical course was marked by several perianal and cutaneous fistulae and repeated abscesses in the retroperitoneum. The second case had more limited disease involving the left and transverse colon. Lesional tissues from both cases were studied by light and electron microscopy. Light microscopic appearance was characterized by the presence of large numbers of histiocytes with typical intracytoplasmic Michaelis-Gutmann bodies. Ultrastructurally, the histiocytes had numerous phagolysosomes and several Michaelis-Gutmann bodies seen as round structures with concentric rings of calcification. These appeared to be derived from large phagolysosomes. In one of our cases, intracytoplasmic clusters of bacillary bodies were also seen within malacoplakic histiocytes.