Abdominal actinomycosis.

A 59-year-old, healthy Croatian presented with a slowly growing tumor in the left lower abdomen, which was slightly painful on compression. He complained of neither dyspepsia nor fever. There were no pathologic findings in laboratory analysis, particularly no elevation of leukocytes or C-reactive protein. MRI of the abdomen (T1w, fat saturated, and iv-contrast) shows a diffuse contrast enhancing mass of the left abdominal wall (Figure 1a, arrow) with infiltration of the peritoneal cavity (Figure 1b, arrow). Because a malignant process was suspected the patient underwent abdominal surgery and excision of the tumor. Histopathological examination showed chronic-fibrosing and granulocytic, abscess-forming inflammation with Gram- and PAS-positive bacteria, corresponding to the diagnosis of chronic actinomycosis (Figure 1c). Following surgery, the patient was treated 1 month with iv and 6 more months with oral penicillin. The patient remained well 1 year after surgery. Actinomycosis is a rare, chronic granulomatous disease, which affects most commonly the cervicofacial and abdominal area. Actinomycetes are filamentous, gram-positive, anaerobic bacteria and commensal inhabitants of the oral cavity and intestinal tract; however, they acquire pathogenicity through invasion of the breached tissue. Because of its rarity and non-specific symptoms, abdominal actinomycosis is usually diagnosed postoperatively since most patients undergo exploratory laparotomy for a suspected neoplasm.