Splenosis is a well-known entity, caused by autotransplantation of splenic tissue as a result of trauma or splenectomy. Patients are generally asymptomatic, and this entity is diagnosed during routine diagnostic imaging. Cystic changes in splenic implants have been defined before but, as to our knowledge, radiological demonstration of cystic components has not been published in the literature. It is well-known that unusual locations of the splenic implants create diagnostic problems, sometimes leading to unnecessary surgical interventions. In this report splenosis, mimicking a renal tumour, with cystic changes in the biggest splenule, and diagnosis with ferrumoxide-enhanced MRI is presented.