Obesity is considered a strong risk factor for renal cell carcinoma, the most common primary renal malignant neoplasm. An association between renal cell carcinoma and obesity has been reported in numerous trials. Several potential mechanisms may be responsible for the risk of renal cell carcinoma in obese subjects. We report the cases of two patients, submitted to bariatric malabsorbtive surgery, who presented a renal clear cell carcinoma several months after the operation. The diagnosis was made by routine postoperative ultrasound examination and confirmed by computed tomography in both cases. Both were treated surgically. Our approach after diagnosis of cancer consisted in evaluation of the patient's immunological, metabolic and nutritional status to establish whether it was a case of real malnutrition or an oncological risk condition. We judged that restoration of original gastrointestinal continuity was not necessary. In the literature, we found no evidence of an association between a cancer histotype and bariatric surgery. Confirming the association between renal cell carcinoma and morbid obesity, these case reports indicate the importance of imaging control, especially with non-invasive diagnostic studies, in high-risk cancer patients, such as obese patients, to detect lesions incidentally at an early stage. After a thorough review of the literature data, we consider bariatric patients a suitable group to be assessed for an early diagnosis of various types of cancer, detectable at preoperative or postoperative screening. Weight loss and continuous instrumental exams are conditions favourable to an early diagnosis. Guidelines regarding the management of oncological patients with a history of bariatric surgery are indispensable.