The frequency of neuroendocrine cell hyperplasia in patients with pulmonary neuroendocrine tumours and non-neuroendocrine cell carcinomas

Aims: To evaluate the frequency of neuroendocrine cell hyperplasia (NEH) in resected neuroendocrine tumours and non-neuroendocrine cell carcinomas and to study its relationship to selected clinical parameters. Methods and results: Random blocks without tumour from resected typical carcinoids (TCs, n = 46), atypical carcinoids (ACs, n = 14), large cell neuroendocrine carcinomas (LCNECs, n = 18), small cell carcinomas (SCLCs, n = 22), adenocarcinomas (ADENOs, n = 26) and squamous cell carcinomas (SCCs, n = 18) were stained for CD56 and evaluated for linear proliferations, cell aggregates (> 4 CD56+ cells), and tumourlets (< 5 mm with basement membrane invasion). There was a statistically significant difference between the frequency of NEH in all neuroendocrine tumours (TC/AC/LCNEC/SCLC, 35/100, 35%) (P = 0.009) when compared with non-neuroendocrine carcinomas (ADENO/SCC, 6/44, 14%) and in the frequency of NEH in TC (21/46, 46%) versus all other tumours (AC/LCNEC/SCLC/SCC/ADENO, 20/98, 20%) (P = 0.001). There was increased frequency of NEH in peripheral TCs (8/13, 62%) compared with central TCs (14/33, 43%) (P = 0.33). There was no association between smoking history and NEH. Clinical and imaging data showed no evidence of an increased frequency of obliterative bronchiolitis in patients with NEH. Conclusions: NEH is significantly increased in the background lung of neuroendocrine tumours when compared with non-neuroendocrine carcinomas, supportive data for NEH having neoplastic potential.