[A case of intrapulmonary lymph node with silicotic nodules in a patient with idiopathic interstitial pneumonia]

A 61-year-old man was admitted to our hospital on October 8, 1991 because of abnormal shadows on chest X-ray at annual checkup at his company. Chest X-ray and CT on admission showed diffuse reticular shadows in bilateral lower lung fields and a nodular opacity approximately 10 mm in diameter in the right lower lung. Since transbronchial lung biopsy was not diagnostic, an open lung biopsy was performed on October 28, 1991. The lung specimens showed diffuse pulmonary fibrosis compatible with usual interstitial pneumonia and an intrapulmonary lymph node containing silicotic nodules. Only 29 cases (including the present case) of intrapulmonary lymph nodes have been reported. Although the causes of intrapulmonary lymph nodes are not clear, smoking is considered to play an important role in the development of pulmonary lymphoid tissue. In our case, the intrapulmonary lymph node contained silicotic nodules. Only several case have been reported to have silicotic nodules in the lymph nodes. As suggested by Kradin, they may be induced by relatively low levels of exposure to dust. Our case also had pulmonary fibrosis (IIP), and is the first reported case of intrapulmonary lymph node associated with IIP. Although it is difficult to determine these two diseases occurred coincidently or not, it is possible that a low level of dust exposure may have contributed to both silicotic nodules in the lymph node and IIP.