Nonmalignant lymphoid disorders of the chest.

Several nonmalignant lymphoid disorders involve the lung parenchyma or the mediastinal or hilar lymph nodes. The pulmonary parenchymal lesions include lymphocytic interstitial pneumonitis, pseudolymphoma, and lymphomatoid granulomatosis. These disorders are generally not accompanied by lymph node enlargement. Lymph nodes (e.g., in the mediastinum and hilum) are involved in lymphadenitis, giant lymph node hyperplasia, and a new and unclearly defined entity called angioimmunoblastic lymphadenopathy. An awareness of the distinction between these reactive disorders and lymphoma is important because the radiologic appearances may be similar. Histologic diagnosis is essential before treatment is initiated. With the exception of angioimmunoblastic lymphadenopathy and possibly of lymphadenitis, involvement of the pulmonary parenchyma associated with radiologic evidence of lymph node enlargement militates against the presence of any of these nonmalignant disorders.