Vessels within vessels in the myometrium.

We have encountered a peculiar vascular architecture in the myometrium wherein arteries are found free-floating within cleft-like spaces. Using different colored dye injections in the uterine arteries and veins, we demonstrated that these spaces are venous channels. This was confirmed by immunoperoxidase staining for CD34, which enhanced the cells lining these spaces. A review of 81 hysterectomy specimens showed that this vascular architecture was present in 42 cases (52%), while it was identified in the parenchyma of only two mastectomy specimens among the 45 specimens from different organs studied. A strong association existed between the presence of this architecture and history of menorrhagia (p = 0.0116). This peculiar vascular architecture might be important in the pathogenesis of menorrhagia and the development of intravenous leiomyomatosis. Pathologists should also be able to recognize these spaces as vascular channels in the event that malignant cells are identified within them.