Renal actinomycosis mimicking renal carcinoma.

The case of a 52-year-old man is reported who presented with night sweats and slight debilitation. Upon CT scan a left-sided renal mass with centrally liquefied areas was detected. The patient underwent nephrectomy for suspected renal cancer with central necrosis. Histologically, the diagnosis of renal actinomycosis was established based on the detection of sulphur granules. Actinomyces israelii is an anaerobic gram-positive bacterium that may cause localized tumour-like infections mainly in the craniocervical region and exceptionally retroperitoneally. Renal actinomycosis is a rare differential diagnosis of renal masses. As nephrectomy may prove hazardous in these cases, the diagnosis should be attempted pre-operatively by ultrasound-guided aspiration and consecutive antibiotic treatment. In selected cases surgery could be avoided at all.