Background: In patients with IPF and ILDs, mediastinal lymph node enlargement (MLNE) is a finding described in a subset of patients. It is associated with accelerated disease progression and increased mortality in these patients. B-cell follicles found in lung tissue, is another common finding. Our hypothesis is that there is an association between MLNE and B-cell follicles in lung tissue in patients with IPF and other ILDs.

Method: Patients having transbronchial cryobiopsies performed as part of an investigation for ILD were included in this prospective observational study. MLNE were assessed in station 7, 4R and 4L. B-cell follicles were assessed on Hematoxylin-Eosin stained specimens. The patients were followed for 2 years. 

Results: Of the 93 patients that were included for analysis, 46% were diagnosed with IPF and 54% were diagnosed with other ILDs. MLNE was found in 26 (60%) of the IPF patients and in 23 (46%) of the non- IPF patients (p=0.164). DLCO was significantly lower (p=0.03) in patients with MLNE compared to patients without MLNE. B-cell follicles were found in 11 (26%) of the IPF patients and in 22 (44%) of the non- IPF patients (p=0.064). There was no association between MLNE and B-cell follicles (p=0.057). In 13 patients, both SLB and cryobiopsies were performed. The presence of B-cell follicles was not consistent when comparing the two different methods.

Conclusion: MLNE is evident in a substantial part of patients with ILD and is associated with lower DLCO at inclusion. No association was found between MLNE and B-cell follicles. In future studies, using larger biopsies for B-cell follicle evaluation should be considered.