We report a case of a 58-year-old female with microscopic extraovarian sex cord proliferations affecting both Fallopian tubes. Molecular analysis showed likely pathogenic germline missense mutations of the KDM5A and KMT2D genes. However, mutations of other genes, including FOXL2 and STK11, were not detected. Our case represents the 12th case of extraovarian sex cord proliferation reported in the literature to date. This is the first time that a molecular genetic analysis of the lesion has been performed, and it showed a wild-type FOXL2 gene, which represents another argument supporting the estimated benign nature of these rare lesions.