Malakoplakia: an unusual cause of lower GI bleeding in a child

Multiple-Organ Involvement of Malakoplakia Mimicking Malignant Neoplasms on 18 F-FDG PET/CT

ABSTRACT

Abdominal contrast-enhanced CT was performed in a 61-year-old man with difficulties of urination and defecation for 4 months, which revealed huge rectal masses involving multiple adjacent organs, suspected as malignant lesions. 18 F-FDG PET/CT was subsequently performed for staging. The images showed intense FDG uptake and slightly hyperdense masses involving rectum, bladder, prostate, left ureter, and the anterior abdominal wall at the level of the pelvic cavity. Histopathological examination confirmed the masses were due to malakoplakia, which displayed as abundant von Hansemann cells aggregated and infiltrated in lesions, with distinctive cytoplasmic inclusions termed Michaelis-Gutmann bodies.

Gastrointestinal Malakoplakia: Clinicopathologic Analysis of 26 Cases

Malakoplakia is an inflammatory process related to defective macrophage response to bacterial infection. To further characterize the clinicopathologic manifestations of gastrointestinal malakoplakia, 26 cases were identified from 6 institutions. Hematoxylin and eosin-stained slides and available stains were reviewed, and pertinent clinicopathologic features analyzed. Sixteen patients were women (62%). Mean patient age was 64 (range: 24 to 83). Sites included the colorectum (n=23), appendix (n=1), and stomach (n=2). Clinical indications for tissue procurement included screening (n=14), tumor resection (n=5), diarrhea (n=1), adenoma surveillance (n=1), ulcerative colitis flare (n=1), abdominal pain (n=1), and appendicitis (1). All cases featured histiocytes with abundant, pale, eosinophilic cytoplasm focally containing Michaelis-Gutmann bodies. The process frequently involved the mucosa (n=19), with architectural distortion in 13 cases. Lymphoid aggregates were present in 18 cases, which were prominent or obscuring in 11 (all colon biopsies) and provoked concern for lymphoma in 2. Associated findings included adenocarcinoma (n=5), adenoma (n=2), gastric hyperplastic polyps (n=1), chemical gastritis (n=1), collagenous colitis (n=1), and active chronic colitis (n=2). In cases with available stains, Michaelis-Gutman bodies were highlighted by Periodic Acid-Schiff with diastase, Von Kossa, and iron stains. Although 2 cases were positive for Tropheryma whipplei antibody, no T. whipplei transcripts were detected on real-time polymerase chain reaction. All patients with available follow-up are alive and well with no additional instances of malakoplakia. Malakoplakia of the gastrointestinal tract is a benign, incidental finding. Although histologic features in the stomach and colon resections are similar to those at other sites, exuberant lymphocytic response in colon biopsies and immunoreactivity with T. whippleii antibody may provoke initial confusion and lead to unnecessary time and resource investment.