Neuroendocrine cell proliferations in lungs explanted for fibrotic interstitial lung disease and emphysema

Using recently proposed pathological criteria, we determined the incidence of neuroendocrine cell proliferation in a series of explants with lung disease. Cases were defined as NECH (≥3 bronchioles with ≥5 endocrine cells), borderline diffuse neuroendocrine cell hyperplasia (DPNECH) (1-3 tumourlets with or without NECH), and DPNECH (≥3 tumourlets with NECH). Endocrine cells were identified by immunohistochemical staining for synaptophysin. There were 65 explants with interstitial lung disease (57 with non-sarcoid fibrotic lung disease, 8 with sarcoidosis), and 21 with centrilobular emphysema. Over one-third of all explant cases demonstrated histological criteria for NECH. There were three cases of DPNECH in the non-sarcoid fibrotic lung disease group (5%) and 20 cases of NECH (35%). The emphysema group had one case of DPNECH (5%), two cases of borderline DPNECH (10%), and seven cases with NECH (33%). The sarcoidosis group had two cases of DPNECH (25%) and three cases of NECH (38%). NECH is common in interstitial lung disease and emphysema. These results suggest that fibrotic lung disease is a predisposing factor for neuroendocrine cell proliferation, in addition to the known risk of epithelial neoplasms.