Malakoplakia of the Gastrointestinal Tract: Prevalence and Clinicopathological Associations

Abstract

Purpose: Malakoplakia (MP) is a rare granulomatous condition thought to result from the insufficient killing of bacteria by macrophages; it is of uncertain clinical significance and can occur at any tissue site. It may be focal or widespread, involving multiple organs. Gastrointestinal MP has been described in association with a variety of conditions such as ulcerative colitis, diverticulitis, adenomatous polyps, and carcinoma. It has been reported to cause rectal bleeding, diarrhea, abdominal pain and simulate polyps or masses. This study reports on the clinicopathologic associations in a series of 8 patients. Methods: This study was conducted at Caris Life Sciences, a specialized gastrointestinal laboratory receiving specimens from outpatient endoscopy centers across the US. Biopsies are interpreted by a group of gastrointestinal pathologists who have achieved a high level of diagnostic agreement by using uniform diagnostic criteria and terminology. We analyzed electronic data from the Caris database, which includes demographic, clinical, and endoscopic information for each patient, the site of origin and the histopathologic report for each biopsy. From a series of over 600,000 patients who underwent upper or lower endoscopies with mucosal biopsies between January 2009 till May 2010, we extracted data for all patients who had a histopathologic diagnosis of MP. Results: There were 8 patients with MP, 7 women and one man, aged 26 to 85 years. Two patients were from LA, and one each from NC, PR, FL, AZ, MD and CA. MP was detected exclusively at a single site in the colon in all cases. No patient had MP in the upper gastrointestinal tract or the small intestine, and none had evidence of diffuse disease. MP was detected in lesions submitted as polyps in all cases: 3 polyps were from the cecum, 3 from the rectum, and one each from sigmoid and ascending colon. Reasons for colonoscopy were: screening for colorectal cancer in 4 patients, bowl habits changes (2 patients), diarrhea (1 patient), and abdominal pain (1 patient). Von Kossa and iron stains showed the diagnostic Michaelis-Gutman bodies in all cases. No previous history of infection, immunosuppression, or other relevant condition was reported in any of the patients. Conclusion: This series confirms that MP is an extremely rare condition, with a prevalence of <0.8 in 100,000 patients with gastrointestinal mucosal biopsies. MP was restricted to the colon in all cases. Clinical presentations were varied: four patients were asymptomatic and the others had changes of bowel habits that may not necessarily be related to MP. All cases were detected in polypoid formations. No MP was identified in “classic” cold climate states/territories.