Case report: primary actinomycosis of external oblique muscle.

A 67-year-old man had actinomycosis with primary involvement of the abdominal wall, which is rare. His chief complaint was an enlarging, hard, nontender mass in the right lower quadrant of the abdomen. The mass had been present for two weeks and measured 11 X 8 cm. An x-ray film of the chest, barium studies of the gastrointestinal tract, and an intravenous pyelogram showed no abnormalities. Excisional biopsy was performed, and the findings were consistent with Actinomyces israelii infection. There was no evidence of underlying bowel disease or break in continuity of the mucous membrane. The patient responded well to a three-month course of penicillin therapy.