A 44-year-old woman presented with a large pelvic mass. Pathology revealed a granulosa cell tumour of the left ovary. The patient was followed after surgery with inhibin B levels and interval imaging. Six years later, she began to experience severe back pain. A vertebral biopsy was positive for metastatic granulosa cell tumour. She underwent radiation to the spine. Inhibin B levels began to rise and, several months later, a CT scan showed a large heterogeneous mass essentially replacing the left kidney. She underwent an open left radical nephrectomy. Pathology revealed a 12 cm cystic nephroma with a 5 cm nodule of metastatic granulosa cell tumour. Immunohistochemistry demonstrated that the mass was inhibin and oestrogen receptor positive. This is a novel presentation of these coexisting pathologies. This unique case sheds light on the possibility of induction of cystic nephroma by the altered hormonal environment created by a granulosa cell tumour metastasis.