Fine-needle aspiration (FNA) of an abdominal wall mass malakoplakia mimicking malignancy: a case report

Introduction/Objective Malakoplakia is a granulomatous disease of infectious etiology that affects immunosuppressed individuals. It commonly involves the genitourinary tract, but the involvement of other systems and organs has been reported. Gram-negative bacterial infections are mostly the responsible agent, with Escherichia coli found in approximately 80% of cases. Malakoplakia can present clinically and radiologically as a malignancy. Methods/Case Report We present a case of a 16-year-old male with a history of acute liver failure requiring liver transplantation due to autoimmune hepatitis. He was admitted with concerns for rejection, and he was found to have an abdominal wall mass. MRI studies showed a lobulated, solid, and cystic mass measuring 11.0 x 4.9 x 1.9 cm in the right abdominal wall. The mass was extending through all the layers of the abdominal wall and protruding into the abdominal cavity with mass effect on the liver, encasing the common bile duct, hepatic artery and main portal vein, concerning for malignancy, versus a possible infectious process. Ultrasound-guided FNA and biopsy were performed. The Diff-Quik and Papanicolaou-stained smears showed abundant foamy macrophages with numerous granular intra- and extracellular slightly refractile inclusions (4-10 um), rare multinucleated giant cells, and fibroblasts. A Von Kossa stain highlighted the targetoid inclusions consistent with Michaelis-Gutman bodies. Additional stains were performed on the core needle biopsy, and the histiocytes were positive for CD68 and CD163. Stains for keratins, CD45, HSA, CD1A, and Langerin were negative. No acid-fast or fungal microorganisms were identified on AFB and GMS stains, respectively. The final diagnosis was malakoplakia, with no evidence of malignancy. Results (if a Case Study enter NA) NA Conclusion Fine-needle aspiration cytology is useful in establishing a fast diagnosis of malakoplakia and excluding malignancies.