To investigate evidence that lymph node silicosis can precede parenchymal silicosis. The study population was comprised of 264 deceased male uranium miners for whom two or more of four pathologists agreed on the presence or absence of silicosis in lymph nodes and lung parenchyma. We had work histories and silica exposure estimates. Twenty percent of the miners had lymph node silicosis only, 4% had parenchymal silicosis only, and 39% had both. Silica exposure was lower for miners with lymph node silicosis only than for those with both lymph node and parenchymal silicosis. Lymph node silicosis was associated with parenchymal silicosis after adjustment for silica exposure. Our results are consistent with silicosis potentially occurring in lymph nodes before the parenchyma. Lymph node damage could impair silica clearance and increase the risk for parenchymal silicosis.
