Misleading diagnosis of retroperitoneal actinomycosis

A 34-year-old woman presented with a left-sided suprarenal space-occupying lesion on sonography. Culture of material obtained during sonographic-guide d puncture of the retroperitoneal lesion yielded a mixed flora of Actinomyc es and Peptostreptococcus. Initially, a misleading diagnosis of an adrenal pheochromocytoma was initiated by highly positive metaiodobenzylguanidine s cintigraphy after chemical chemistry vanillylmandelic acid (VMA) test showe d elevated values for adrenaline and its derivatives. Retroperitoneal actin omycosis with yet unproven spread into thoracic and cervical compartments i s a particular unusual presentation of an infection with these organisms. B ecause it may mimic subacute infections of malignant masses in terms of cli nical and laboratory findings, radiological diagnosis of this entity may be difficult. The diagnosis was based on results of culture and the response of the patient to long-term penicillin-derivate therapy after surgical drai nage of the suprarenal abscess formation.