Sequential ultrasonographic imaging of changes from a giant hematoma to atrophic changes in a case of Breus' mole

Breus' mole is a massive subchorionic thrombohematoma (MST) that arises below the chorionic plate on the fetal side of the placenta. Breus' mole requires careful perinatal management because of the high incidence of severe fetal growth restriction (FGR) and intrauterine fetal demise (IUFD). However, the mechanism of its development remains unclear, and there are no reports to date of continuous changes in hematomas. Herein, we report a case of Breus' mole in which ultrasonographic changes of an MST were observed during pregnancy. A 40-year-old pregnant patient presented to our hospital with FGR (-2.5 standard deviation), a hematoma with a high-echoic lesion, and an extremely thickened placenta at 22 weeks of gestation. The giant hematoma remained highly echoic with a placental thickness of 7 cm at 27 weeks of gestation; however, it gradually combined with high- and low-echoic lesions and progressed to a low-echoic lesion at 29 and 30 weeks of gestation. Finally, it got to shrink and almost disappeared at 34 weeks of gestation, during which placental thickness was 3.5 cm. At 34 weeks of gestation, a male infant, weighing 1230 g, was delivered by Caesarean section. The placenta weighed 289 g, and a 5-cm-long and 2-cm-thick dark brown area was observed under the chorionic villus near the umbilical cord attachment site. Histopathology revealed a subchorionic hematoma in the same area, consistent with Breus' mole. We observed ultrasonographic changes in the giant hematoma from high-to-low-echoic, associated with atrophic changes in the placental tissue. The sequential ultrasonographic imaging may be one of the factors in understanding Breus' mole pathophysiology.