Background: Renal malacoplakia is a very rare chronic inflammatory disorder characterized by specific infiltration of tissue by inflammatory cells, and presents similar radiological characteristics to those of renal cell carcinoma.
Case Report: A 54-year old woman, with a 37-year history of smoking, weight loss, anorexia, asthenia, and night sweats, was included in an antiangiogenesis clinical trial. Clinical signs of inflammation were apparent in the right lumbar region without functional limitations. Previous imagery identified a mass infiltrating the lower pole of the right kidney, extending to the psoas, perinephretic region and ganglia. Biological testing revealed inflammation and a urinary tract infection, treated with ciprofloxacin. Based on histology of a renal puncture biopsy, clear cell carcinoma with oxyphilic cells was suspected but not confirmed by immunohistochemistry.
Urine analysis was positive for Escherichia Coli. Computed tomodensitometry revealed three masses (right kidney, between right psoas and the inferior vena cava, and right psoas) and a second puncture biopsy confirmed malacoplakia. After successful antibiotherapy, a right-sided nephrectomy was performed. The patient now shows no evidence of disease.
Conclusions: This case underscores the importance of excluding the differential diagnosis of renal malacoplakia before undertaking partial or total nephrectomy and/or initiating neoadjuvant treatment for renal cell carcinoma.

Keywords: Malacoplakia, kidney, diagnosis