Actinomycosis is a rare chronic disease characterized by a suppurative and granulomatous response to Actinomyces infection, often complicated by fibrotic scarring and mass formation. 1. Bullock W.E. Actinomycosis. in: Goldman L. Bennett J.C. Cecil textbook of medicine. 21st ed. W.B. Saunders, Philadelphia2000: 1714-1715 Google Scholar Differential diagnosis can be complex because multiple systems can be involved and the clinical picture may resemble several diseases, including malignancies. 2. Waaddegaard P. Dziegiel M. Actinomycosis mimicking abdominal neoplasm. Acta Chir Scand. 1988; 154: 315-316 PubMed Google Scholar Diagnostic evaluation is laborious, frequently requiring multiple radiologic, endoscopic, and surgical procedures. 3. Putman H.C. Dockerty M.B. Waugh J.M. Abdominal actinomycosis: an analysis of 122 cases. Surgery. 1950; 28: 781-801 PubMed Google Scholar Abdominal-pelvic localization is a severe manifestation of actinomycosis, because it can extend by contiguity to organs such as the liver or the spine. 4. Davies M. Keddie N.C. Abdominal actinomycosis. Br J Surg. 1973; 60: 18-22 Crossref PubMed Scopus (72) Google Scholar Colonic involvement typically is caused by infiltration of Actinomyces through minute mucosal lesions and can occur after surgical procedures 5. Piper M.H. Schaberg D.R. Ross J.M. Shartsis J.M. Orzechowski R.W. Endoscopic detection and therapy of colonic actinomycosis. Am J Gastroenterol. 1992; 87: 1040-1042 PubMed Google Scholar or as complication of appendicitis or, more rarely, diverticulitis. 6. Deshmukh N. Heaney S. Actinomycosis at multiple colonic sites. Am J Gastroenterol. 1986; 81: 1212-1214 PubMed Google Scholar Less frequently, the bowel wall may be seeded by contiguity when peritoneal infection is present. 7. Yeguez J.F. Martinez S.A. Sands L.R. Hellinger M.D. Pelvic actinomycosis presenting as malignant large bowel obstruction: a case report and a review of the literature. Am Surg. 2000; 66: 85-90 PubMed Google Scholar The endoscopic appearance is non-specific, usually submucosal nodules or masses involving the ileocecal region, the appendix, or, less frequently, the rectosigmoid region. 5. Piper M.H. Schaberg D.R. Ross J.M. Shartsis J.M. Orzechowski R.W. Endoscopic detection and therapy of colonic actinomycosis. Am J Gastroenterol. 1992; 87: 1040-1042 PubMed Google Scholar , 6. Deshmukh N. Heaney S. Actinomycosis at multiple colonic sites. Am J Gastroenterol. 1986; 81: 1212-1214 PubMed Google Scholar , 8. Yang S.H. Li A.F.Y. Lin J.K. Colonoscopy in abdominal actinomycosis. Gastrointest Endosc. 2000; 51: 236-238 Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar , 9. Kim J.C. Ahn B.Y. Kim H.C. Yu C.S. Kang G.H. Ha H.K. et al. Efficiency of combined colonoscopy and computed tomography for diagnosis of colonic actinomycosis: a retrospective evaluation of eight consecutive patients. Int J Colorectal Dis. 2000; 15: 236-242 Crossref PubMed Scopus (17) Google Scholar A case is presented of abdominal-pelvic actinomycosis characterized by an unusual endoscopic finding of multiple bulging submucosal nodules confined to the sigmoid colon without evidence of diverticular disease or other potential mucosal defect.