Actinomycose colique : à propos d’un cas et revue de la littérature

When a rare simultaneous infection simulates a local extension of a rectal cancer: a case report

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.

[Bacterial colitis]

The question of whether there are inflammatory changes in colorectal biopsy specimens is frequently asked, especially when the patient reports diarrhea or when the mucosa is reddened on endoscopy. The pathologist first has to find out whether there is, in fact, an increase in the inflammatory infiltrate of the colorectal mucosa which warrants the diagnosis of inflammation. If so, the second challenge is to ascertain the etiology of these inflammatory changes, in particular to differentiate between infectious and non-infectious causes. In principle, we can distinguish forms of colitis with distinct morphological hallmarks confirming the diagnosis (e.g. microscopic detection of the causative organism, as well as lymphocytic or collagenous colitis) from other forms of colitis which have a characteristic pattern of findings not necessarily allowing to deduce the etiology (e.g. infectious colitis without microscopic evidence of the germ vs. inflammatory bowel disease). The present article discusses the pathomorphology and differential diagnosis of the most important forms of bacterial colitis.