Elemental analysis of hilar and mediastinal lymph nodes in idiopathic pulmonary fibrosis

Elemental analysis of hilar and mediastinal lymph node tissues was performed to determine whether some inhaled atmospheric elements are implicated in the pathogenesis of idiopathic pulmonary fibrosis (IPF). IPF was divided into two types; typical and atypical, according to our criteria. Lymph nodes were selected as the study material rather than lung tissue, because inhaled elements are concentrated in the hilar and mediastinal lymph nodes, and increase in lung weight due to fibrosis may influence the estimated values of element per unit weight of lung tissue. The hilar and mediastinal lymph nodes collected from 40 IPF cases and 43 non-IPF control cases were examined to determine the concentration of 13 elements in 100 mg dry tissue, using the X-ray fluorescent analysis method. For aluminium, 50 mg dry tissue was examined by an atomic absorption analysis method. Among the 14 elements, Ni in IPF lymph nodes showed a significantly higher level than in control nodes (mean +/- SD: 8.2 +/- 21.3 ppm versus 1.1 +/- 2.1 ppm, respectively. p < 0.01). No difference in each of the examined elements was noted between smokers and non-smokers or between typical and atypical IPF cases. Exogenous elements such as Ni may play a role as triggering substances in the pathogenesis of IPF.