What are the most common causes of mediastinal lymphadenopathy?
The four most common causes of radiographically detectable mediastinal lymphadenopathy are sarcoidosis, lymphoma, metastatic tumor, and granulomatous infections. In younger patients with bilateral hilar and mediastinal lymphadenopathy, sarcoidosis should be the diagnosis of exclusion because it is the most common cause. In older individuals, lymphoma and metastatic tumor are the most common causes of mediastinal lymphadenopathy. It would seem logical that any pulmonary infection could lead to mediastinal lymphadenopathy; however, only granulomatous infections commonly cause mediastinal or hilar lymphadenopathy. These include primary tuberculosis, histoplasmosis, cryptococcosis, and coccidioidomycosis.