Ollier disease is a condition affecting 1 in 100,000, characterized by multiple endochondromas (1). It is caused by sporadic mutations in isocitrate dehydrogenase-1 and 2, although the exact pathogenesis is unknown (1). There have been 11 case reports of juvenile granulosa cell tumour associated with Ollier disease (2,3), however the pathophysiological link between these is unclear. Some postulate that this represents a generalized mesodermal dysplasia in patients with Ollier disease (2). Here we present a case of a 75-year-old woman with Ollier disease, who presented with a large pelvic mass. The histological analysis of this mass was challenging, requiring input from several pathologists over several sites. The diagnosis of sarcomatoid adult granulosa cell tumour was rendered after consensus review. This is the first case, to our knowledge, of an association between adult granulosa cell tumour and Ollier disease. Interestingly, the patient also had an incidental finding of a renal oncocytoma. Ollier disease has also been associated with various other musculoskeletal, CNS, lung, breast and renal tumours (4) but there are no reports of an association with renal oncocytoma.