FLCN gene mutations cause Birt-Hogg-Dubé (BHD), a hereditary renal cancer syndrome. A classic triad of findings characterizes BHD, which includes cutaneous fibrofolliculomas, pulmonary cysts, and renal tumors. The condition is caused by germline mutations in the FLCN gene, which encodes folliculin; the function of this protein is largely unknown, although FLCN has been linked to the mTOR pathway. Somatic second-hit mutations identified in BHD-associated renal tumours are consistent with a tumour-suppressor function for FLCN. Individuals with BHD have about a 34% lifetime risk for renal cancer, most frequently diagnosed in the fifties. Additionally, male FLCN mutation carriers are twice as likely to be affected as female carriers. Approximately 50% of BHD-related renal tumors manifest as a chromophobe/oncocytic hybrid: 34% chromophobe, 9% clear cell, 5% oncocytoma, and 2% papillary.