Abstract
Multiple synchronous malignancies are rarer than metachronous ones. Primary synchronous breast and renal cancer is even rare. Such a case requires strict exclusion of possible metastasis to either site and to confirm the primary nature of each malignancy for better outcome of management and survival benefit. Multiple primary synchronous malignancies may be due to shared genetic mutations if any common carcinogenic factor cannot be found. The role of estrogens in cases in which human renal carcinoma is associated with other primary tumours involving steroid-hormone target tissues, is tentative and can only be hypothesised due to paucity of such data in literature. One should consider the possibility of concomitant dual or multiple primary tumours in a patient presented with mass lesions at various sites, especially if one of the sites is the kidney. We present a case report of a patient with synchronous primary breast and renal cancer.