[Pseudotumoral pelvic actinomycosis : one should think of it]

Actinomycosis is a rare chronic disease caused by a group of anaerobic Gram positive bacteria. It may mimic a neoplasia at various anatomical levels. A pelvic localization is exceptional but has an increasing incidence since the use of intrauterine devices. In such cases, pelvic actinomycosis may present as a gynecological or a lower colonic malignancy. For all atypical clinical, with a prominent infectious or inflammatory context, the diagnosis of actinomycosis must be suggested and discussed with the pathologist to whom the biopsy will be submitted. In the absence of a preoperative diagnosis, an inadequately aggressive pelvic surgery might be performed and rendered particularly complex due to the adherent and diffusely inflammatory pattern of the disease. The treatment of choice remains a long-term therapy with antibiotics that leads to a complete clinical and radiological response in the majority of cases. We report the case of a 27-year-old woman with a clinical and radiological diagnosis of rectal carcinoma but with limited preoperative biopsy that revealed a pelvic actinomycosis and allowed a conservative and successful antibacterial treatment.