Retroperitoneal Malakoplakia Mimicking Metastatic Disease

Abstract Malakoplakia is a rare inflammatory granulomatous disease that can produce a tumor-like appearance in nearly any organ system. Imaging findings of malakoplakia overlap with malignancy and tissue sampling are typically required for definitive diagnosis. We present a case of a 66-year-old woman with a previous history of liver adenocarcinoma status post resection that subsequently developed an intensely FDG-avid retroperitoneal mass on surveillance imaging. CT-guided biopsy of the mass demonstrated Michaelis-Gutmann bodies, supporting the diagnosis of malakoplakia. The patient underwent antibiotic treatment with complete resolution of the mass.