Are lung cysts in renal cell cancer (RCC) patients an indication for FLCN mutation analysis?

Renal cell cancer (RCC) represents 2-3% of all cancers and is the most lethal of the urologic malignancies, in a minority of cases caused by a genetic predisposition. Birt-Hogg-Dubé syndrome (BHD) is one of the hereditary renal cancer syndromes. As the histological subtype and clinical presentation in BHD are highly variable, this syndrome is easily missed. Lung cysts--mainly under the main carina--are reported to be present in over 90% of all BHD patients and might be an important clue in differentiating between sporadic RCC and BHD associated RCC. We conducted a retrospective study among patients diagnosed with sporadic RCC, wherein we retrospectively scored for the presence of lung cysts on thoracic CT. We performed FLCN mutation analysis in 8 RCC patients with at least one lung cysts under the carina. No mutations were identified. We compared the radiological findings in the FLCN negative patients to those in 4 known BHD patients and found multiple basal lung cysts were present significantly more frequent in FLCN mutation carriers and may be an indication for BHD syndrome in apparent sporadic RCC patients.