The coexistence of several tumours in the same patient is a rare phenomenon and corresponds to the multiple primary tumour (MPT) syndrome. The most frequently diagnosed MPT include gastrointestinal tumours associated with urological tumours. Overexpression of the STAG1 gene could explain the development of several solid tumours and could be the origin of the multiple primary tumour syndrome. A suspicious renal mass discovered at the same time as a documented cancer is usually a malignant lesion and may justify combined radical surgical treatment. The authors report the natural history of a suspicious renal mass in a patient with primary gastric tumour corresponding to a MPT syndrome. They recall and discuss the epidemiology, pathophysiology, diagnosis and treatment of MPT.