Among the 30 tumour entities investigated, we identified significant GPR19 expression (mean IRS value ≥ 3) only in lung tumours, especially in those with a neuroendocrine background, such as TC, AC, and SCLC, and in medullary thyroid carcinomas, parathyroid adenomas, and pheochromocytomas, which also belong to the neuroendocrine tumour entities. Here, GPR19 is linked to small cell lung carcinoma.