CUP is characterized by the finding of a metastasis the starting point of which (the primary tumour) is unknown. Typically, one finds an enlarged lymph node in the neck, a swelling in the throat or in the stomach, a filling in the skin or a tumour detected somewhere in the body during an X-Ray examination, an endoscopy or the like. In spite of a search applying multiple techniques, the primary tumour remains unknown in 70-80% of the patients.