PLAG1 and smooth muscle tumor: PLAG1 promoter swapping and subsequent activation is reported as playing a key role in the development of pleomorphic adenomas of the salivary gland, lipoblastomas, hepatoblastomas, and some leukemias, and PLAG1 overexpression has been found in uterine leiomyomas, leiomyosarcomas, and other smooth muscle tumors [4, 65, 66].