Postoperative abdominal wall actinomycosis mimicking malignancy: a case report and literature review

Actinomycosis is an uncommon chronic bacterial infection that may present as an infiltrative mass mimicking malignancy. Abdominal wall involvement, particularly after abdominal surgery, is rare and may pose a considerable diagnostic challenge.

A focused narrative review of PubMed was conducted to identify reports of abdominal and abdominal wall actinomycosis, focusing on clinical presentation, predisposing factors, diagnosis, treatment, and outcomes. Eleven relevant case reports were included in the comparative analysis.

We report a 72-year-old woman with a history of left hemicolectomy for colorectal carcinoma who developed a progressively enlarging painful mass of the left abdominal wall. Computed tomography revealed an infiltrative soft tissue lesion extending toward adjacent retroperitoneal structures, raising suspicion for recurrent malignancy or soft tissue sarcoma. Surgical excision was performed. Histopathological (HP) examination revealed "sulfur granules" with radiating filamentous structures and surrounding Splendore-Hoeppli material within a dense suppurative inflammatory reaction, associated with granulation tissue and reactive fibrosis. These findings supported the diagnosis of abdominal wall actinomycosis. The patient received prolonged Penicillin-based antibiotic therapy, with a favorable outcome.

Abdominal wall actinomycosis should be considered in the differential diagnosis of infiltrative masses, particularly after abdominal surgery. HP examination and appropriate special stains are essential for distinguishing this rare infection from malignancy and other mimics.