Actinomycosis mimicking a pancreatic head neoplasm: A case report

Actinomycosis is a chronic suppurative disease caused by a filamentous, Gram-positive, facultative anaerobic bacterium Actinomyces. Abdominal actinomycosis accounts for 10 to 20% of reported Actinomyces infections and pancreatic involvement is extremely rare.

We report the case of a 64-year-old man who presented with a 3-week history of abdominal pain, nausea, weight loss, and icterus. Abdominal CT scan revealed a 3.5 cm heterogeneously enhanced mass of the pancreatic head, associated with mild dilation of the main bile duct and the Wirsung duct. The diagnosis of pancreatic head malignancy was highly suspected and surgical management was decided. Intraoperatively, a 3 cm indurated mass of the pancreatic head was found. Whipple's procedure was performed. Histopathological examination revealed pancreatic actinomycosis.

Pancreatic actinomycosis is extremely rare. To our knowledge, only 18 cases have been reported in the English literature to date. It commonly presents as a slow-growing mass with bile and pancreatic ducts obstruction, which can mimic malignancy. Therefore, it has often been misdiagnosed and over-treated with futile surgery, when medical treatment based on antibiotherapy is the only required treatment.

We reported a rare observation of surgical management of actinomycosis mimicking a pancreatic head neoplasm. As clinical and radiological findings are nonspecific, the accurate diagnosis can only be made by histology. Through our case, we aim to highlight the importance of preoperative suspicion of pancreatic actinomycosis, given the still relevant morbidity of pancreatic resections.