We report a case of a patient who presented with a left sided inguinal swelling. Ultrasound examination clearly revealed a bilateral inguinal lymphoma. In addition, a renal cell carcinoma was diagnosed through ultrasound. The differences in texture between lymph nodes and renal tumour as well as the even concentric swelling of the lymph node sinus permitted a clear cut differentiation between the two entities. CT could not provide this clear distinction. Despite some controversy several case reports as well as a few retrospective studies showed an increased coincidence of renal cell carcinoma and malignant lymphoma. However, a pathophysiological connection has not yet been discovered. This report presents another case of synchronous appearance of renal cell carcinoma and malignant lymphoma and demonstrate the relevance of ultrasound in the discrimination between the two clinical entities. It is essential for physicians performing either sonography and/or CT to be aware of this coincidence to avoid misdiagnosis of lymphadenopathy in patients with renal cell carcinoma as metastasis and, vice versa, renal tumours in lymphoma patients as renal manifestation of the lymphoma.