Abstract
PURPOSE: To describe the clinicopathological spectrum of genitourinary malakoplakia (MPL) and to evaluate the feasibility and clinical impact of metagenomic pathogen detection (MetaPath) performed on archival formalin-fixed paraffin-embedded (FFPE) tissue. PATIENTS AND METHODS: Clinical imaging, histopathology, immunohistochemistry, special stains and MetaPath results were retrospectively analysed in five MPL cases diagnosed between January 2019 and August 2025. RESULTS: The cohort comprised four men and one woman with a median age of 65.4 years. Four lesions arose in the prostate and one in the bladder. Histology showed chronic granulomatous inflammation with numerous eosinophilic histiocytes containing 5-10 µm targetoid Michaelis-Gutmann bodies. CD68 and CD163 were diffusely positive; PAS and iron stains highlighted the inclusions. MetaPath identified pathogens in 3/5 (60%) FFPE specimens (Escherichia coli in two, Pseudomonas aeruginosa in one). Antibiotic regimens were adjusted according to MetaPath results. After a median follow-up of 6 months (range 4-8) all patients remained symptom-free. CONCLUSION: MPL is frequently misdiagnosed as malignancy. MetaPath can reliably detect pathogens in archival tissue and guide targeted antimicrobial therapy, representing a valuable adjunct to conventional culture.