[Rare manifestation of actinomycosis as retroperitoneal space-occupying lesion]

Actinomycosis has to be included in the differential diagnosis of retroperitoneal masses especially when surrounding tissue is infiltrated. We present a 40 year old male patient with the rare manifestation of retroperitoneal actinomycosis. The definitive treatment consisted of surgical drainage and long-term penicillin therapy resulting in complete healing. Special features in clinical symptomatology and problems concerning diagnosis of actinomycosis are discussed.