Although it has been reported that estrogen receptor (ER) expression coupled with glucose metabolism using ER imaging agents for PET, such as 16α-[18F]-fluoro-17β-estradiol and FDG PET, is useful for the differential diagnosis of leiomyomas and leiomyosarcomas, there were still some overlapping cases [21]. The gene discussed is ESR1; the disease is leiomyosarcoma.