Uterine Junctional Zone and Endometrial Cancer

Abstract

PURPOSE: The human uterus consists of the ontogenetically and phylogenetically older endometrium, the adjacent junctional zone and the more recent outer myometrium. This understanding of uterine zonal anatomy could provide an answer to the question why the risk of lymph node metastasis increases abruptly when an endometrial adenocarcinoma invades more than 50 % of the myometrial wall. MATERIAL AND METHODS: High resolution vaginal ultrasound was performed in 100 healthy postmenopausal women and their zonal anatomy was documented. In a meta-analysis the relationship between the depth of myometrial invasion by endometrial cancer and the rate of regional lymph node metastases was analyzed. RESULTS: In postmenopausal women the mean diameter of the junctional zone of the myometrium was found to be almost exactly half the inner diameter of the myometrium. Our meta-analysis confirmed the existence of a threshold whereby, if an endometrial adenocarcinoma invaded more than 50 % of the myometrial wall, this resulted in a more than 5-fold higher prevalence of lymph node metastasis. CONCLUSION: Endometrial cancer rarely results in lymph node metastasis as long as the disease is confined to the junctional zone of the myometrium. The dissimilarity between the inner and outer myometrial layers, based on their very different phylogenetic and ontogenetic origins, might be of interest for further research.