MRI differentiation of pneumonia-like mucinous adenocarcinoma and infectious pneumonia.

Objective: To evaluate the role of MRI water-sensitive sequences in the differential diagnosis between pneumonia-like mucinous adenocarcinoma and infectious pneumonia. Subjects and methods: Twenty-three patients with pneumonia-like mucinous adenocarcinoma and 30 patients with infectious pneumonia underwent computed tomography (CT) and MRI. Two blinded and independent readers evaluated CT and MR images using a 3-level confidence scale in two separate sessions. Results were tested for statistical significance using the Fisher's exact test and the Cohen's k test. Results: On CT, the two readers respectively made correct diagnoses of mucinous adenocarcinoma in 17 out of 23 cases (73.9%), and in 15 out of 23 cases (65.2%). A correct diagnosis of infectious pneumonia was made in 22 out of 30 cases (73.3%), and in 24 out of 30 cases (80.0%). On MRI, both readers made correct diagnoses of mucinous adenocarcinoma in 23 out of 23 (100%) cases, and of infectious pneumonia in 30 out of 30 (100%) cases. Fisher's exact test showed a significant difference in the diagnosis of mucinous adenocarcinoma between MRI and CT for both readers, P = 0.01 for reader 1 and P = 0.002 for reader 2, respectively. A good agreement (k = 0.73) was found between the two readers on CT evaluation, whereas an almost perfect agreement (k = 1.00) was found for MRI. Conclusions: MRI with "water-sensitive" sequences should be added in the diagnostic protocol of every patient with pulmonary consolidation suspected to be mucinous adenocarcinoma.