Histological analysis of the uterine junctional zone as seen by transvaginal ultrasound

Objective This study aimed to investigate the histology of the subendometri al halo, the junctional Zone between the endometrium and myometrium. Methods Thirteen ex vivo uteri removed for treatment of menorrhagia were st udied. In each case, the subendometrial halo, as seen by transvaginal ultra sound was marked using a Nottingham breast location biopsy needle. A standa rd histological examination was performed. Full thickness blocks of the ant erior uterine wall were taken and standard serial 5-mu m tissue sections we re prepared from Each block. Subsequent morphometric analysis followed stai ning with Feulgen reagent, using a CAS 200D quantitative image analysis sys tem. Additionally, anti-CD31, an antibody stain for vascular endothelium, t eas used. Results The histological examination showed the subendometrial halo to cons ist of apparently normal myometrium. Morphometric analysis demonstrated a g reater total nuclear area in the subendometrial halo than the outer myometr ium, but no difference in individual nuclear size between the two zones. CD 31 stained a greater total area in the inner myometrium. Conclusions These results suggest that the subendometrial halo is a distinc t compartment of the myometrium comprising tightly packed muscle cells with an increased vascularity. Such architecture would increase the density of this tissue layer, altering its acoustic impedance, and account for its ech openic appearance on ultrasound.