BACKGROUNDTo analyze the causes of computed tomographic misdiagnosis of pulmonary carcinoma.

METHODSFrom September 1991 to January 2002, 45 cases of pulmonary carcinoma misdiagnosed by CT were analyzed retrospectively. Twenty-six cases of pulmonary tuberculosis and 15 cases of pulmonary pneumonia misdiagnosed as pulmonary carcinoma by CT were studied as control subjects. All of these cases were confirmed by surgery and clinical course. The CT appearances of these cases were independently reviewed in a double blind method by three experienced radiologists. Then they discussed together in order to search for the factors of CT misdiagnosis and formed a consensus interpretation.

RESULTSForty-five cases of pulmonary carcinoma were misdiagnosed as pulmonary tuberculosis in 19 cases, pneumonia in 14 cases, abscess in 4 cases, pleural mesothelioma in 2 cases, normal in 2 cases, and others in 4 cases. The fundamental manifestations of misdiagnosed cases were lobar or segmental shadows (26 cases), solitary mass or nodule (19 cases).The reasons of CT misdiagnosis were very confusing. The main factors were:(i) Missed diagnosis (2 cases, 4.5%). One case had an endobronchial mass and another had the erosion of rib. (ii) Twenty-four cases (53.3%) due to mis interpretation and lack of experience. (iii) The manifestations in CT were atypical (19 cases,42.2%).

CONCLUSIONSNot identifying accurately the CT appearances and excessively emphasizing the specificity of some signs are the main causes of the misdiagnosis. A reasonable and careful CT examination, summarizing analysis combined with clinical findings, and the accumulation of diagnostic experience will help to reduce the CT misdiagnostic rate of pulmonary carcinomas.