Neuroendocrine tumours in the lungs such as large-cell neuroendocrine carcinoma (LCNEC) are a rare occurrence in the Netherlands. Pathologists, oncologists and lung cancer oncologists are all confronted with various problems regarding the diagnosis and treatment of LCNEC. Firstly, making the diagnosis is difficult due to the lack of standards for small biopsies. Secondly, there is no clear advice regarding systemic treatment of patients with metastatic LCNEC. Based on these problems, this thesis studied temporary adjustments to the diagnosis and treatment of LCNEC in approximately 1,000 patients in the Netherlands. The accuracy of the diagnosis was checked by performing a biopsy. Finally, we examined which type of chemotherapy may result in better survival rates in patients with LCNEC undergoing treatment in primary care settings.