Papers of the Week

Extramedullary hematopoiesis (EMH) is a physiological compensatory mechanism that develops in response to ineffective or insufficient hematopoiesis. Although the liver and spleen are the most common sites, EMH may occur anywhere in the body. Peri-renal involvement in EMH is quite rare and mimics tumoral lesions. To our knowledge, 12 peri-renal EMH cases have been reported in the literature so far.  A 57-year woman was admitted to our hospital with non-specific abdominal pain. She had a history of chronic renal failure. On physical examination, diffuse abdominal tenderness and mild rigidity were detected. Blood tests revealed bicytopenia and elevated acute phase reactants. On non-contrast abdominal computed tomography (CT) scan, two peri-renal mass lesions of 4.5 cm and 4 cm were detected incidentally on the right side. Tumoral lesions were considered in the differential diagnosis, and magnetic resonance imaging (MRI) and positron emission tomography-computed tomography (PET-CT) were performed. Lesions showed mild hypermetabolic activity (SUVmax: 4,68) on PET-CT images. For the definitive diagnosis, an ultrasound-guided core needle biopsy was performed. The histopathological examination was consistent with EMH. This case aims to highlight the peri-renal involvement of EMH, which mimics renal and peri-renal malignancies.  Key Words: Extramedullary hematopoiesis, Kidney, Computed tomography, Magnetic resonance imaging.