[Pseudomalignant primary renal actinomycosis after ureterosigmoidostomy. A case report].

Actinomycosis is a chronic infectious disease caused by a gram-positive anaerobe. The bacterial disease is known to predominantly affect the oropharyngeal mucosa and soft tissues as well as the gastrointestinal tract. However, renal involvement by actinomycosis is exceedingly rare. Thus, renal actinomycosis is usually diagnosed by means of histopathological assessment of nephrectomy specimens because affected patients seek medical care due to (peri-) renal mass lesion clinically mimicking cancer. To best of our knowledge, we present the first case worldwide reporting on a 65-year-old man diagnosed with renal actinomycosis following ureterosigmoidostomy in whom nephrectomy was performed due the clinical suspicion of renal cancer (stage cT4). Subsequently, calculated antibiotic therapeutic regimens were initiated after the diagnosis was suspected by the pathologist. During the entire postsurgical follow-up comprising a total of 6 months, the patient did not experience any local or systemic recurrence. In summary, detailed information concerning the etiology, the clinical symptoms as well as diagnostic and therapeutic options are discussed in our case report.