• Collections of apparently benign lymphocytes which lack the usual invasive characteristics of true lymphoma

• Lack of invasion of extrapulmonary tissues in this disease

• Mixed cellular infiltration (as opposed to uniform cellular infiltration of true lymphoma) with mature lymphocytes predominating

• Other lesions characterized by the presence of mature lymphocytes

• LIP

• Castleman’s disease–lymph node hyperplasia

• Lymphomatoid granulomatosis

• Well-differentiated lymphocytic lymphoma

• Classically, there is no involvement of the lymph nodes in the hilum or mediastinum

• May be associated with Dilantin administration (as is true lymphoma and benign lymph node hyperplasia)

• Asymptomatic

 X-ray  

• Dense infiltrate

• Invariably has air bronchogram

• May also have nodules, segmental consolidation or diffuse interstitial infiltration