Abdominal actinomycosis by Actinomyces shaaliae georgiae mimicking neoplasia

We report the case of a 77-year-old male who presented with a three-week history of constitutional symptoms, accompanied by an indurated epigastric mass measuring 10 × 7 cm with a 4 cm phlyctenae, exhibiting local and systemic inflammatory responses.

Abdominal computed tomography demonstrated focal thickening of the transverse colon with a poorly defined inflammatory lesion extending to the abdominal wall and a collection suggestive of colo-cutaneous fistula. The clinical and imaging findings raised a strong suspicion of malignancy. Microbiological culture from drainage material isolated Actinomyces shaaliae georgiae, further reinforcing the suspicion of neoplastic disease due to the tumor-like presentation.

Initial management included antimicrobial therapy and percutaneous drainage. Surgical exploration revealed a stony hard mass without cleavage planes, adherent to adjacent organs. Histopathological examination excluded malignancy, confirming an infectious process caused by A. shaaliae georgiae. The patient received prolonged antibiotic therapy, resulting in a favorable clinical outcome.

To our knowledge, this represents the first reported case of abdominal actinomycosis caused by A. shaaliae georgiae with this unique presentation. Actinomycotic lesions form purulent foci surrounded by extensive fibrosis, creating tumor-like masses that clinically and radiologically mimic neoplastic processes. This case expands the clinical spectrum and microbiological repertoire of A. shaaliae georgiae, emphasizing the critical importance of maintaining high clinical suspicion, implementing multidisciplinary diagnostic approaches, and ensuring appropriate antimicrobial management in abdominal actinomycosis to avoid unnecessary surgical interventions and improve patient outcomes.