Mediatinal lymph node, histoplasmosis

Histoplasmosis is a fungal infection prevalent through out the Mississippi River Valley. The characteristic lesion is the granuloma seen here in the hilar lymph nodes. It most commonly infects the lung and usually does not spread. In the immunosuppressed patient it can disseminate. At higher power it would be possible to see the yeast forms of H. capsulatum within the macrophages scattered throughout the granuloma. Note the ring of lymphocytes forming the periphery of the granuloma.