We report 3 cases of a hitherto undescribed phenomenon in women aged 46 to 49 in which there was replacement of the myometrium or cervical stroma by an accumulation of hypocellular myxoid stromal material containing bland spindle-shaped cells and small blood vessels. In all cases, this change was conspicuous, and in 2 it was multifocal and widespread, resulting in consideration of an infiltrative myxoid mesenchymal neoplasm. Immunohistochemistry revealed a characteristic immunophenotype with diffuse strong positivity with CD34 and CD10 but no immunoreactivity with the smooth muscle markers desmin, alpha-smooth muscle actin, and h-caldesmon. In comparison, 3 cases of uterine myxoid leiomyoma were positive with smooth muscle markers and negative with CD34 and CD10. We believe the lesion we describe to be an unusual pseudoneoplastic, possibly degenerative, phenomenon. The patients past medical histories were unremarkable, with no history of connective tissue disease (myometrial myxoidosis has rarely been described in association with lupus erytematosus) or Carney's syndrome. Two patients had been prescribed local or systemic progestogens, raising the possibility of an association with these compounds. Pathologists should be aware of this unusual pseudoneoplastic phenomenon to avoid a misdiagnosis of a neoplastic lesion.