[Pulmonary actinomycosis presenting as a mass shadow with a cavity on chest radiography].

A 53-year-old woman was admitted with diabetes mellitus. After admission, a tumor shadow was detected by chest radiography and blood was found in her sputum. Despite further investigations, no definite diagnosis was made. Pulmonary wedge resection was performed because malignancy could not be excluded. Histological examination of the resected lung specimen led to the diagnosis of pulmonary actinomycosis. In Japan, 59 cases of pulmonary actinomycosis were reported between 1964 and 1993. These reports indicate that many cases of this disease are diagnosed by histological examination of resected lung specimens. Pulmonary actinomycosis has become even rarer recently because of the development of chemotherapy. We report this case and discuss the relevant literature.