Though thymic NETs have long been associated with MEN1, this is the first time that LOH at the MEN1 locus has been shown in multiple thymic tumors demonstrating that, despite previous unsuccessful attempts to find LOH (Teh et al. 1998, Gibril et al. 2003, Pan et al. 2005), the Knudson two-hit hypothesis also applies to the thymic tumors of MEN1 syndrome, with LOH as the apparent mechanism of tumorigenesis (Knudson 1971). Here, MEN1 is linked to multiple endocrine neoplasia type 1.