Sustentacular cells in pulmonary neuroendocrine tumours

Aims: To determine the prevalence of sustentacular cells across the range o f pulmonary neuroendocrine rumours: typical and atypical carcinoid tumours and large cell and small cell neuroendocrine carcinomas, Methods and results: Sustentacular cells were sought in 80 pulmonary neuroe ndocrine tumours by immunolabelling for S100 protein, nerve growth factor r eceptor and glial fibrillary acidic protein, Inratumoural macrophages and L angerhans cells were identified with the KP 1 (CD68) and CD1A antibodies. S 100-positive sustentacular cells were present in 25 of 30 typical carcinoid s, 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 prevalence being clearly relat ed to grade of differentiation and, in particular, to the degree of archite ctural organization. Conclusions: Sustentacular cells are often found in pulmonary neuroendocrin e rumours, especially better-differentiated lesions with a well-developed a rchitecture, their prevalence clearly reflecting the degree of structural o rganization. Whether their prevalence is a useful prognostic indicator with in a particular group of such tumours, such as the atypical carcinoids or t he large cell carcinomas, as appears to be the case with paragangliomas, is unclear.