Lymphocytic interstitial pneumonia identified as lymphoma of mucosa associated lymphoid tissue.

The widespread interstitial pulmonary infiltration in two patients, showing the clinical, radiological and histological features of lymphocytic interstitial pneumonia (LIP), has been characterized by histological and immunological criteria as malignant lymphoma of follicle centre cell (FCC) origin with plasmacytic differentiation. One patient also had malignant lymphoma of the parotid glands which had been present for many years and was previously considered benign (benign lymphoepithelial lesion). The other patient had a long history of Sjögrens syndrome. The lymphomas in these patients are presented as typical examples of malignant lymphoma of mucosa-associated lymphoid tissue.