Cancer of unknown primary (CUP) is characterized as a clinical disorder where patients present with histologically conrmed metastatic cancer for which standard diagnostic investigations failed to identify the primary site [1]. Median age at presentation is 65 years and is more common in men. It accounts for 3-5% of all human cancers with an overall incidence per 100,000 population per year of 7-12 cases in the US, 4-6 in Switzerland and 18-19 in Australia. It is considered to be the seventh or eighth most frequent malignant tumour.