ABSTRACT
BACKGROUND: Actinomycosis is a rare chronic infection caused by Actinomyces. The abdominopelvic localization of this pathology makes preoperative diagnosis extremely exceptional. The following report is the case of a patient treated for adenocarcinoma of the middle rectum associated with mesorectal actinomycosis. The diagnosis of actinomycosis was made postoperatively. CASE PRESENTATION: A 69-year-old Caucasian male patient was admitted for rectal bleeding. Clinical and paraclinical assessment revealed a middle rectum adenocarcinoma with local extension in the mesorectum. The patient underwent an anterior resection of the rectum by laparotomy after neoadjuvant chemoradiotherapy. Postoperative follow-up was simple. Pathological study of the specimen noted complete sterilization of the rectal adenocarcinoma and the presence of large foci of suppurative necrosis containing actinomycotic grains in the mesorectum. CONCLUSION: Abdominopelvic actinomycosis is a rare pathology and has therefore rarely been dealt with. This issue can lead to unnecessary and mutilating surgery. We report an exceptional coincidence of rectal adenocarcinoma and mesorectal actinomycosis mistaken for mesorectal extension of the cancer.