[818] Mycobacterium Abscessus Granulomatous Prostatitis

AY Chuang, MH Tsou, SJ Chang, LY Yang. Koo Fundation Sun Yat-Sen Cancer Center, Taipei, Taiwan

Background: In 2007, several patients who received radical prostatectomy for prostate cancers experienced poor wound healing. Mycobacterium abscessus had been cultured from the debridement specimens and acid fast stain (AFS)-positive bacilli were also found in radical prostatectomies (RPs).
Design: From 2007 to 2009, all 180 RPs had been reviewed and 12 cases with morphologies suspicious of Mycobacterium abscessus granulomatous prostatitis (MAGP) were identified. AFS, fungal stain and culture from preserved fresh tissue were also performed. The aim of this study was to evaluate the pathologic features, differential diagnosis and clinical significance of MAGP.
Results: The characteristic morphologic feature of MAGP was suppurative necrotizing granulomatous inflammation extensively involving the prostate. The centers of MAGP were large areas of neutrophilic abscess and necrotic debris which were surrounded by histiocytes (epithelioid, foamy, and multinucleated giant cells), lymphocytes, plasma cells, and eosinophils. Lobular distribution with extension of mixed inflammatory infiltration into dilated and ruptured ducts is evident in the surrounding areas. In these 12 patients, the percentage of involved prostate area ranged from 10% to 80% (mean: 39%, median: 37.5%). Involvement of extraprostatic soft tissue and seminal vesicle/vas deferens were found in 9 (75%) and 4 (33.3%) cases, respectively. AFS-positive bacilli were identified in five (41.7%) RPs. Eleven patients had fresh tissue specimens stored at -150 centigrade. Mycobacterium abscessus had been successfully cultured and confirmed in 8 patients. No MAGP was found in the TRUS-biopsy specimens in all patients. After radical prostatectomy, 8 patients (66.7%) experienced prolonged poor wound healing (> 1 month) with urethra-rectal fistula formation in one patient and pelvic abscess in another.
Conclusions: MAGP could be easily missed due to unfamiliar with this rare infectious granulomatous prostatitis. Besides, mixed inflammatory infiltrates with lobular distribution in MAGP can resemble non-specific granulomatous prostatitis. Mixed inflammatory infiltrates with extensive involvement of the prostate (>10%), large neutrophilic necrotic centers and involvement of extraprostatic soft tissue, seminal vesicles and vas deferens are important clues for performing AFS or culture. Familiarity with the morphology with adjunctive use of special stains can minimize misdiagnosis of MAGP.
Category: Genitourinary (including renal tumors)

Wednesday, March 24, 2010 9:30 AM

Poster Session V # 106, Wednesday Morning


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