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Diagnosis and Discussion: Case 1145

Final Diagnosis

Placenta accreta spectrum disorder (PASD grade 3A), massive subchorionic thrombohematomas of the fetal surface of the placenta (Breus mole), marginal placenta previa, and ascending acute infection (acute cervicitis and acute chorioamnionitis [maternal inflammatory response stage 2 grade 2 and fetal inflammatory response stage 2 grade 2]).

Discussion

This patient had multiple placental pathologies associated with abnormal placentation and preterm premature rupture of membranes. The discussion will focus on placenta accreta spectrum disorder (PASD) and massive subchorionic thrombohematoma (Breus mole).

Placenta accreta spectrum disorder (PASD) is defined as abnormal placentation resulting in various degrees of placental adherence and invasion of the myometrium.1 Overall incidence of PASD has continued to increase along with the rates of cesarean section, with reported rates of approximately 3 per 1,000 deliveries in the United States. 1,2  

Diagnosis is based on the microscopic examination of the placental bed, requiring extended areas of absent decidualized endometrium between placental trophoblast and/or villous tissue and myometrium.1 This includes foci with chorionic villi directly attached to the superficial myometrium or a layer of fibrinoid and intermediate trophoblast between chorionic villi and the myometrium.1 Additionally, degenerated myofibers, interstitial edema, chronic inflammation, remodeling of myometrial vessels (intimal thickening or with hemosiderin-laden macrophages), and hemorrhage (retromembranous and subchorionic/intervillar) can be seen.1,3 Grading is based on the degree of gross invasion and is performed exclusively on hysterectomy or partial myometrial resection specimens.1 The grading is as follows:

  1. PASD Grade 1—non-invasive: grossly adherent placenta with a smooth placental-myometrial interface and uniform myometrial thickness without thinning.
  2. PASD Grade 2—superficial invasion: irregular placental-myometrial interface with preservation of the outer 25% of myometrial wall thickness.
  3. PASD Grade 3A—deep invasion: irregular placental-myometrial interface with involvement of outer 25% of myometrial thickness but with intact serosa.
  4. PASD Grade 3D—deep invasion with serosal disruption: deeply invasive placental with disruption of uterine serosa.
  5. PASD Grade 3E—deep invasion with involvement of adherent extra-uterine structures: placental invasion of adjacent organs or extrauterine fibroadipose tissue.1

It should be noted that PASD Grade 3 categories 3B and 3C (urinary bladder and pelvic tissue/organ invasion, respectively) were removed since both are covered under the category 3E.1

On the other hand, the abnormally invasive placenta (AIP) system establishes the following groups:

  1. Placenta accreta vera: placental villi directly implanted onto the myometrium.
  2. Placenta increta: placental villi invading deeper into the myometrium.
  3. Placenta percreta: placental villi penetrating through the uterine serosa.3,4

However, according to the expert panel recommendations presented by Hecht et al., the PASD grading should be utilized instead of the AIP system to improve reproducibility and reduce inconsistencies. 1 Majority of cases fall under the accreta group (~60%), followed by percreta (~20%), and lastly, increta (~15%).1  

Pathogenesis of PASD remains unclear; however, a possible pathophysiological mechanism includes defects of the endometrial-myometrial interface with abnormal vascularization secondary to uterine scarring and resulting abnormal decidualization. 1,2 Other authors have proposed a pathway involving excessive trophoblastic invasion during placental formation. 2,3,4

Diverse risk factors for developing PASD include—most importantly—previous history of cesarean section or curettage, but also advanced maternal age, multiparity, Asherman syndrome, prior uterine radiation or surgery (e.g., myomectomy), endometrial ablation, leiomyomas, uterine anomalies, smoking, and placenta previa.1,2 It has been reported that a patient with six or more cesarean sections has a 28 times higher risk of developing PASD as opposed to a patient with only one previous cesarean section.5 Interestingly, the increased incidence of PASD in cases of placenta previa further highlights the potential role of poor decidualization in the pathogenesis of PASD.4 Although this patient was young, several risk factors were identified, such as two prior curettages and the presence of a marginal placenta previa.

Prenatal diagnosis and subsequent surgical planning are key in improving maternal and fetal morbidity and mortality associated with PASD. Prenatal imaging—mainly ultrasound (US) but also magnetic resonance imaging (MRI)—is usually the preferred modality to establish a diagnosis given most patients are asymptomatic.1,2 Diagnosis of PASD by ultrasound has reported sensitivity and specificity of approximately 90% and 96%, respectively.2 However, it should be noted that this imaging modality cannot accurately predict the depth of placental invasion unless there is involvement of adjacent organs.2 Some characteristic sonographic features include multiple lacunae within the placenta, irregular placental-myometrial interfaces, and thinning of the myometrium.2 Nonetheless, placental lacunae can be observed in normal placentas and not every case of PASD will display lacunae. It has been established that the greater the number of placental lacunae, the greater the risk for PASD.2 Less reliable sonographic findings suggestive of PASD are the loss of the hypoechoic retroplacental zone, increased placental vascularity, abnormalities of the uterine serosa-urinary bladder interface, retroplacental myometrial thickness less than 1 mm, and the presence of bridging vessels between the placenta and the urinary bladder.2 MRI findings suggestive of PASD include dark intraplacental bands on T2-weighted imaging, disruption of the zone between the uterus and the placenta, and disorganized placental blood vessels.2 This modality is used to supplement US findings in cases of posterior or lateral placental implantation and to estimate the depth of invasion.2 Despite these imaging tools, it is estimated that around 50-66% of cases remain undiagnosed.3

PASD is associated with significant maternal morbidity and mortality, mainly secondary to obstetrical hemorrhage.1,2 Approximately 70% of patients with PASD are managed with cesarean hysterectomy, which is performed ideally before the onset of labor to improve maternal outcomes.2,6 Among the many complications of PASD include adjacent organ damage, postoperative bleeding, uterine inversion or rupture, consumptive coagulopathy, acute respiratory distress syndrome, multisystem organ failure, and maternal death, to name a few.2,4,6 Additional management with blood transfusion is expected in around 85% of women undergoing cesarean hysterectomy.2,6 The overall mortality rate of this procedure is 1.6%, but can increase up to 10% in cases of placental invasion through uterine serosa.2,6 Conversely, neonatal outcomes are related to the gestational age at delivery and not the depth of placental invasion.2

Massive subchorionic thrombohematoma—also termed Breus mole—was first described in 1892 as a large maternal blood clot that separates the chorionic plate from the villous chorion.7 This is a rare phenomenon with an estimated incidence of 0.03%-0.08%.7 Although there is no current consensus definition for Breus mole, at our institution we use the proposed criteria of fetal surface distortion with greater than 1 cm in thickness and/or encompassing greater than 50% of the fetal surface. We also require fetal surface distortion. Its pathogenesis and etiology are poorly understood.7,8 Reported maternal risk factors include cardiovascular disease, hypertension, thrombophilia, and diabetes.8,9 Monosomy X (Turner syndrome) and elevated alpha-fetoprotein (AFP) levels have been reported as fetal risk factors.8,9 Complications and outcomes depend on its size and location, and include intrauterine fetal growth restriction (IUGR), preterm delivery, spontaneous abortion, vaginal bleeding, placental abruption, preeclampsia, and intrauterine fetal death (IUFD).7,8,10,11 Although challenging, diagnosis can occasionally be made via US, displaying hemorrhage as large echogenic areas near the chorionic plate and placentomegaly.7 Given the high rate of abortion and premature delivery, management includes tocolytics and antibiotics.10 Perinatal mortality is largely associated with extreme prematurity and IUGR.11

This young female presented with preterm labor in a setting of preterm premature rupture of membranes and abnormal placentation. Several risk factors for the development of PASD were identified, most notably the presence of placenta previa and a history of prior curettages, which likely resulted in abnormal decidualization and associated placental invasion into the myometrium. Prenatal diagnosis was performed with US, which allowed for surgical planning in efforts to reduce the patient’s morbidity and mortality. Incidentally, a Breus mole was identified. Preterm delivery has been linked to Breus mole, however this could also have resulted from the ascending infection after the preterm premature rupture of membranes. Given the complex and sometimes unclear pathophysiology of these diseases, establishing an initial abnormality would be challenging and most likely represent a complex interaction of many processes resulting in abnormal placentation. Despite the multiple placental pathologies identified, the patient recovered and was discharged soon after delivery.

References

  1. Hecht, J. L., Baergen, R., Ernst, L. M., Katzman, P. J., Jacques, S. M., Jauniaux, E., Khong, T. Y., Metlay, L. A., Poder, L., Qureshi, F., Rabban, J. T., 3rd, Roberts, D. J., Shainker, S., & Heller, D. S. (2020). Classification and reporting guidelines for the pathology diagnosis of placenta accreta spectrum (PAS) disorders: recommendations from an expert panel. Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc, 33(12), 2382–2396. https://doi.org/10.1038/s41379-020-0569-1
  2. Horgan, R., & Abuhamad, A. (2022). Placenta Accreta Spectrum: Prenatal Diagnosis and Management. Obstetrics and gynecology clinics of North America, 49(3), 423–438. https://doi.org/10.1016/j.ogc.2022.02.004
  3. Bartels, H. C., Postle, J. D., Downey, P., & Brennan, D. J. (2018). Placenta Accreta Spectrum: A Review of Pathology, Molecular Biology, and Biomarkers. Disease markers, 2018, 1507674. https://doi.org/10.1155/2018/1507674
  4. Khong T. Y. (2008). The pathology of placenta accreta, a worldwide epidemic. Journal of clinical pathology, 61(12), 1243–1246. https://doi.org/10.1136/jcp.2008.055202
  5. Marshall, N. E., Fu, R., & Guise, J. M. (2011). Impact of multiple cesarean deliveries on maternal morbidity: a systematic review. American journal of obstetrics and gynecology, 205(3), 262.e1–262.e2628. https://doi.org/10.1016/j.ajog.2011.06.035
  6. Shellhaas, C. S., Gilbert, S., Landon, M. B., Varner, M. W., Leveno, K. J., Hauth, J. C., Spong, C. Y., Caritis, S. N., Wapner, R. J., Sorokin, Y., Miodovnik, M., O'Sullivan, M. J., Sibai, B. M., Langer, O., Gabbe, S. G., & Eunice Kennedy Shriver National Institutes of Health and Human Development (NICHD) Maternal–Fetal Medicine Units Network (MFMU) (2009). The frequency and complication rates of hysterectomy accompanying cesarean delivery. Obstetrics and gynecology, 114(2 Pt 1), 224–229. https://doi.org/10.1097/AOG.0b013e3181ad9442
  7. Miyagi, M., Kinjo, T., Mekaru, K., Nitta, H., Masamoto, H., & Aoki, Y. (2019). Massive Subchorionic Thrombohematoma (Breus' Mole) Associated with Fetal Growth Restriction, Oligohydramnios, and Intrauterine Fetal Death. Case reports in obstetrics and gynecology, 2019, 9510936. https://doi.org/10.1155/2019/9510936
  8. Baergen, R. N. (Ed.). (2013). Placental pathology. Elsevier.
  9. El-Agwany A. S. (2017). Large Subchorionic Hematoma: Breus' Mole. Journal of medical ultrasound, 25(4), 248–250. https://doi.org/10.1016/j.jmu.2017.09.006
  10. Giri, V., Cheema, Q., & Mulay, A. (2011). Early-onset severe growth restriction and placental abruption associated with Breus mole. International journal of gynaecology and obstetrics: the official organ of the International Federation of Gynaecology and Obstetrics, 113(1), 81–82. https://doi.org/10.1016/j.ijgo.2010.11.006
  11. Alanjari, A., Wright, E., Keating, S., Ryan, G., & Kingdom, J. (2013). Prenatal diagnosis, clinical outcomes, and associated pathology in pregnancies complicated by massive subchorionic thrombohematoma (Breus' mole). Prenatal diagnosis, 33(10), 973–978. https://doi.org/10.1002/pd.4176