Sustentacular cells in pulmonary neuroendocrine tumours

AimsTo determine the prevalence of sustentacular cells across the range of pulmonary neuroendocrine tumours: typical and atypical carcinoid tumours and large cell and small cell neuroendocrine carcinomas.Methods and resultsSustentacular cells were sought in 80 pulmonary neuroendocrine tumours by immunolabelling for S100 protein, nerve growth factor receptor and glial fibrillary acidic protein. Intratumoural macrophages and Langerhans cells were identified with the KP 1 (CD68) and CD1A antibodies. S100‐positive sustentacular cells were present in 25 of 30 typical carcinoids, 20 of 25 atypical tumours, six of 10 large cell carcinomas and six of 15 small cell lesions. They were most numerous in the typical carcinoids but very few in the small cell carcinomas, their prevalance being clearly related to grade of differentiation and, in particular, to the degree of architectural organization.ConclusionsSustentacular cells are often found in pulmonary neuroendocrine tumours, especially better‐differentiated lesions with a well‐developed architecture, their prevalence clearly reflecting the degree of structural organization. Whether their prevalence is a useful prognostic indicator within a particular group of such tumours, such as the atypical carcinoids or the large cell carcinomas, as appears to be the case with paragangliomas, is unclear.