TFE3-rearranged renal cell carcinoma with osseous metaplasia and indolent behaviour

TFE3-rearranged renal cell carcinoma (RCC) is a rare but well characterised histological subtype of RCC with an aggressive clinical course and propensity for late metastases. Osseous metaplasia is an uncommon but well documented finding in clear cell, papillary and chromophobe RCC. We present the first case of a TFE3-rearranged RCC to be found harbouring metaplastic bone in a 47-year-old woman who presented with a slowly enlarging left flank mass over a 10 year period. This case report adds to the clinicopathological description of TFE3-rearranged RCC and suggests that larger studies are required to fully elucidate the prognosis of these tumours.