In antiquity, physicians related depression or melancholic humour to cancer's pathogenesis. Galen (130-201 AD), sustained that melancholy could give rise to a tumour and his theory was repeated by the Byzantine and Arab physicians. In the 19th century, malignancy and depression became synonymous and people attributed their cancer to sadness. In 1893, the London surgeon Hebert Snow (1847-1930), performed an epidemiological study in order to clarify that link. The results revealed a probable connection. His work was followed by several large scale prospective studies some of which identified depression as a risk factor for cancer where others found no association. However, a possible explanation could be given by our current knowledge in immunology: inflammation and nonspecific immune activation play a role in the pathophysiology of depression and cancer growth.