Folliculin (FLCN) is a tumor suppressor whose function is lost in Birt-Hogg-Dubé syndrome (BHD), a disorder characterized by renal cancer of multiple histological types including clear cell carcinoma, cutaneous fibrofolliculoma, and pneumothorax.
Additional molecular genetic testing revealed somatic mutations and epigenetic events in genes typically associated with these specific histologic tumor types: oncocytoma harbored a second FLCN mutation (intron 12, IVS12+4 C>T), oncocytic papillary carcinoma harbored promoter methylation of FLCN, and a missense mutation in the MET gene (P246L), whereas clear cell carcinoma harbored inactivating VHL mutation (5-base pair deletion in exon 2) and VHL gene promoter methylation.