Abstract
Pulmonary typical carcinoid (TC) is a low-grade, rare lung cancer of neuroendocrine origin. Currently, there is very little information available about the immune cell composition in TC tumours. Here, we analysed by flow cytometry resected tumours from four never-smoker female patients with TC. Twelve distinct immune cell types were identified in TC tumours. The most abundant immune cells were CD8+ T cells, CD4+ T cells, B cells and macrophages, which represented 19.8%, 17.7%, 11.5% and 11% of all tumour-infiltrating CD45+ leucocytes, respectively. Natural killer (NK) cells (8.8%) and neutrophils (3.9%) were also common. Three types of dendritic cells (DCs) were identified (plasmacytoid DCs, CD1cDCs, and CD141DCs) which together constituted 1.4% of all immune cells in TC tumours. Small populations of basophils (1.2%), mast cells (0.8%) and eosinophils (0.6%) were also present. Notably, the percentage of leucocytes (of all living cells) was much lower in TC tumours compared to high-grade non-small cell lung cancer (NSCLC) tumours and also compared to non-cancerous lung tissue. We conclude that TC tumours are relatively non-inflammatory, although the immune landscape was found to be very complex.
Highlights
Pulmonary carcinoids are rare neuroendocrine tumours of the lungs with two subtypes: low-grade typical carcinoid (TC) and intermediate-grade atypical carcinoid.[1,2,3] Carcinoids represent 1%-2% of all primary lung cancers[4,5] and, contrary to most airways malignancies, are not linked to tobacco smoking
The percentage of CD45+ leucocytes in TC tumour was lower compared to non-cancerous distal lung, but the general composition was similar
The only immune cell type previously identified with certainty in TC tumours are the cytotoxic CD8+ T cells.[15,16,17]
Summary
Pulmonary carcinoids are rare neuroendocrine tumours of the lungs with two subtypes: low-grade typical carcinoid (TC) and intermediate-grade atypical carcinoid.[1,2,3] Carcinoids represent 1%-2% of all primary lung cancers[4,5] and, contrary to most airways malignancies, are not linked to tobacco smoking. To the best of our knowledge, cytotoxic CD8+ T cells represent the only immune cell type that has been identified with certainty in TC tumours so far.[15,16,17] Katsenelson et al found CD1a+ and CD83+ dendritic cells (DCs) in high-grade small cell lung cancer but none in bronchial carcinoid tumours.[18]. In this short report, we used multiparameter flow cytometry to analyse the immune cell content in resected tumours from four patients with TC. As many as twelve distinct immune cell types were identified, the percentage of immune cells of all living cells in TC tumours was relatively low
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