STK11 and Cowden disease: As one of the hamartoma syndromes, BHD shares many clinical features (such as follicular hamartomas, mucosal fibromas, and internal malignancy) with Cowden syndrome (CD, affected gene PTEN), Peutz-Jeghers syndrome (PJS, affected gene LKB1), and tuberous sclerosis complex (affected genes TSC1/TSC2) [14], [15], [16].