A 22-year-old woman was hospitalized for progressive right lumbar pain and tumefaction, fever and malaise of several months’ duration. The patient had a 12-year history of intermittent symptoms of urinary tract infections. An exhaustive study searching for a cause of the recurrent infections was not done. Her family history was negative for renal diseases. On examination there was tenderness, redness and a fistulous tract in the right lumbar region. Laboratory investigations showed a normal renal function. Urinalysis revealed numerous leukocytes. An abdominal computed tomography scan revealed a right kidney displaced and compressed by a well-defined lesion with cystic aspect that is in contact with renal pelvis. Adjacent there was an ill-defined retroperitoneal mass which was in contact with the psoas, extending from the diaphragm to the pelvis, with involvement of the lumbar subcutaneous tissue and connecting to the fistulous tract (Figure ​(Figure1).1). Left kidney appeared normal. A CT-guided percutaneous biopsy of the mass was undertaken. Fig. 1 CT scan revealed a well-defined capsulated mass with cystic aspect in contact with the right renal pelvis. In retroperitoneum there is an ill-defined mass in contact with the psoas and extending to paravertebral space, lumbar subcutaneous tissue and skin ... The biopsy revealed clusters of histiocytes with ample granular eosinophilic cytoplasm. In many of them were one or more round basophilic structures measuring between 1 μm and 10 μm approximately 1 μm and 10 μm; some were laminated, others appeared homogeneous, and others had a dense central core with a targetoid appearance (Figure ​(Figure2).2). Nephrectomy of the right kidney demonstrated focal congenital cystic renal dysplasia. Fig. 2 Collections of large histiocytes with granular eosinophilic cytoplasm: von Hansemann cells. The cytoplasm contains abundant basophilic inclusions with a variable size: Michaelis–Gutmann bodies. Some of them are laminated and others have targetoid ... Malakoplakia is a chronic inflammatory process which most often affects the urinary tract, but it may involve a variety of other organs. Malakoplakia is the result of an acquired defect in macrophage function causing impairment of bactericidal activity. The large macrophages that are present at sites of infection (von Hansemann cells) exhibit numerous secondary lysosomes containing partially digested organisms. Fusion and calcification of these lysosomes result in the formation of intracytoplasmic bodies called Michaelis–Gutmann bodies, considered pathognomonic of malakoplakia [1,2]. Conflict of interest statement. None declared.