Differential diagnosis of lymphocytic interstitial pneumonia and malignant lymphoma on high-resolution CT

OBJECTIVE. Lymphoproliferative disorders span a spectrum from inflammatory lesions to malignant neoplasms. The purpose of this study was to compare high-resolution CT findings of lymphocytic interstitial pneumonia with those of malignant lymphoma of the chest. MATERIALS AND METHODS. The study included 17 patients with lymphocytic interstitial pneumonia and 44 patients with malignant lymphoma (35 with non-Hodgkin's lymphoma and nine with Hodgkin's disease). Without knowledge of the pathologic diagnosis, two chest radiologists evaluated the frequency and distribution of high-resolution CT findings in both groups of patients. RESULTS. Cysts were more common in patients with lymphocytic interstitial pneumonia (14/17, 82%) than in patients with malignant lymphoma (1/44, 2%) (p < .0001). Air-space consolidation was more commonly seen in patients with malignant lymphoma (29/44, 66%) than in patients with lymphocytic interstitial pneumonia (3/17, 18%) (p < .001). Large nodules (11-30 mm in diameter) were more common in patients with malignant lymphoma (41%) than in patients with lymphocytic interstitial pneumonia (6%). Pleural effusions (25%) were seen only in patients with malignant lymphoma. We found no statistically significant difference in the distribution of lung lesions between patients with lymphocytic interstitial pneumonia and patients with malignant lymphoma. CONCLUSION, On high-resolution CT, cysts are characteristic in patients with lymphocytic interstitial pneumonia, whereas consolidation, large nodules, and pleural effusions are characteristic in patients with malignant lymphoma. These findings on high-resolution CT help differentiate lymphocytic interstitial pneumonia from malignant lymphoma.