Ultrasound detection of lacunae-like image of a cesarean scar pregnancy in the first trimester.

Cesarean scar pregnancy is one of the rare types of ectopic pregnancy. Ultrasonography enables early diagnosis and the successful preservation of the uterus. However, the correct diagnosis of cesarean scar pregnancy can be difficult in some cases. We describe a case of cesarean scar pregnancy that was initially misdiagnosed on the basis of current ultrasonographic criteria. Ultrasonographic images at 9 weeks' gestation demonstrated no gestational sac but did show a bulging mass in uterine wall with irregularly shaped hypoechoic areas, which resembled the lacunae in placenta previa. Color Doppler imaging demonstrated that the lacunae-like areas were richly perfused. Cesarean scar pregnancy was finally diagnosed with magnetic resonance imaging, which showed a lack of myometrium in the lower anterior uterine wall with placental invasion. Histological examination of the uterus after hysterectomy revealed the direct invasion of trophoblasts into the mural zone which had resulted in a deficit of myometrium at the previous cesarean scar. A mass in the myometrium with richly perfused lacunae-like areas should be considered as one of the important ultrasonographic findings indicating cesarean scar pregnancy.