The primary objective of this study is to analyse the concentration dopamine and serotonin in thrombocytes of patients with renal cell carcinoma and neuro-endocrine tumours compared to the concentrations of these catecholamines in healthy volunteers. The concentration dopamine and serotonin in thrombocytes with and without medication will also be evaluated.

• To analyse the concentration catecholamines in thrombocytes of patients with clear cell renal cell carcinoma and low grade neuroendocrine tumours.
• To compare these concentrations with the concentrations catecholamines in thrombocytes of healthy controls.
• To analyse the concentration catecholamines in thrombocytes of patients with clear cell renal cell carcinoma and patients with low grade neuroendocrine tumours with and without medication.

Inclusion Criteria:

• Age 18 years old or older.
• Patients with clear cell renal cell carcinoma with metastases or patients with a low-grade neuro-endocrine tumor with metastases.
• Written informed consent

Exclusion Criteria:

• Use of L-dopa or SSRI.
• Patients with a second primary malignancy.

Patients with clear cell renal cell carcinoma with metastases and patients with low grade neuroendocrine tumours with metastases.