Pulmonary cystadenoma Fetal lung development is one of the determinants of survival after birth, and accurate prenatal diagnosis and evaluation of disorders affecting fetal lung development is important. The most common disorders affecting fetal lung development include cysticercosis adenoma of the lung (CCAM), Bronchopulmonary Sequestration (BPS), congenital diaphragmatic hernia and pleural effusion. The incidence of fetal CCAM accounts for approximately 25% of congenital lung lesions and is the most common. CCAM is due to the overgrowth of the fetal terminal bronchus, which forms a clearly defined lesion in the lung parenchyma, often involving part of the lobe or the entire lung lobe, either unilaterally or on both sides of the lung parenchyma, and 90% of them may develop mediastinal shift. The exact etiology of CCAM is not yet fully understood, but the most common view is that CCAM is a malformation-like lesion, i.e., an overgrowth of one or more tissue components, which may be due to local obstruction of lung development and subsequent overgrowth of developed lung tissue due to unknown factors during fetal lung bud development. According to the pathological changes, the prenatal diagnosis of CCAM by ultrasound is divided into three types: Type I is a large cystic type, in which a cystic mass is seen in the thoracic cavity with a diameter of >2 cm without separation, and lung tissue echogenicity is seen around the cystic mass. Type II is a microcystic type, in which a cystic mass is seen in the thoracic cavity, manifesting as multiple small cysts with a cavity diameter <50px< span="">. Type III is a mixed type, also known as multicystic lung, which is formed by the fusion of smaller cysts with lung tissue, showing enlarged lobes in the affected thoracic cavity with enhanced and uniform echogenicity and mediastinal shift to the opposite side. The pathophysiology of CCAM, which is supplied by the pulmonary circulatory system, is mainly due to the compression of the mass, which leads to the displacement of the mediastinum, and then to the obstruction of venous return, resulting in fetal edema, and to the occupancy of the mass, which leads to the compression of the lungs, resulting in poor lung development. Davenport M et al. summarized a total of 67 cases of prenatally diagnosed fetal chest masses from 1995 to 2001, with a mean gestational age of 21 weeks (19-28 weeks), of which 43% were right-sided, 54% were left-sided, and 3% were bilateral. The macrocystic type accounted for 40%, microcystic type for 52% and mixed type for 8%. While Adzick NS et al in a review of 22 cases of prenatally diagnosed fetal CCAM suggested that microscopic lesions (less than 5 mm) combined with fetal edema suggested a poor prognosis; giant lesions (single or multiple, greater than or equal to 5 mm) without combined fetal edema had a good prognosis; four cases were giant lesions and completely disappeared at subsequent ultrasound follow-up (18%). Diagnosis and evaluation in the fetal period Prenatal diagnosis Prenatal ultrasound, due to its technical maturity, widespread use and ease of monitoring, has become the preferred modality for CCAM. Serial ultrasound studies of fetal thoracic lesions help to define the specific type of these lesions, determine their pathophysiological features, predict clinical outcome and form management opinions based on prognosis. Due to the sensitivity of ultrasound to fetal pulmonary masses, prenatal confirmation of the diagnosis is not difficult, but differentiation from BPS is required, and the application of Doppler to the source of blood supply to the mass can be the main point of differentiation, i.e., the blood supply to the pulmonary circulation in CCAM and the body circulation in BPS. in 1983, Smith et al. reported the first magnetic resonance imaging (MRI) examination of the fetus. Although ultrasound remains the imaging method of choice for fetal examination, with the development of MRI technology and its advantages of no radiological damage, multi-sectional imaging, broad field of view and good soft tissue contrast resolution, it is increasingly becoming an important complement to ultrasound diagnosis. Prenatal MRI has been reported to provide more information about normal and abnormal lung development and to better predict fetal outcome after birth by analyzing and evaluating lung relaxation time and measuring lung volume.MRI has a radiofrequency wavelength of several meters and an energy of only 10-7ev, which is 1/1010 of CT and safer for the fetus.MRI can suggest more details of fetal congenital structural malformations, and MRI is useful in The diagnosis of fetal chest anomalies, especially for atypical lesions, or combined with multiple complex anomalies can compensate for the lack of ultrasound diagnosis and help in the prenatal comprehensive assessment of the fetus and the development of treatment plan after delivery. CCAM is most commonly found between 18 and 26 weeks, and the size of the mass, the rate of change in mass size, and whether it causes fetal edema are important indicators of fetal prognosis. The literature reports a range of normal values for lung volume measured by fetal 3D ultrasound from 16 weeks to 36 weeks to understand the development of fetal lung at each gestational week, providing a valuable reference standard for assessing fetal mass volume and lung dysplasia. The most common method is to calculate the cephalopulmonary ratio (CVR), which is the volume of the lung mass (volume is width*height*length*0.523)/fetal head circumference, and its clinical significance is very different when the CVR is greater or less than 1.6. If the CVR is less than or equal to 1.6, the prognosis is good if there is no edema. For those with CVR greater than 1.6, edema was present in most cases. In cases without edema, the mass tends to decrease gradually after about 25-28 weeks. In contrast, those who develop edema have a high mortality rate. Grethel et al. summarized 15 years of experience with 294 cases of intrauterine interventions for thoracic occupational lesions and combined fetal edema, with a postoperative survival rate of >95% in those without combined fetal edema, and concluded that although the cause of combined fetal edema is not fully understood, the occurrence of fetal edema is indeed related to the volume of the occupational lesion. Therefore, regular monitoring of the fetus with ultrasound is essential. The fetal CCAM is detected prenatally and if it is not combined with fetal edema and the outcome is good, it is a reasonable choice to continue the pregnancy. Delivery is usually after 32 weeks. Conventional spontaneous delivery is used in all cases without symptoms; in cases of mediastinal shift, microcystic, and suspected airway obstruction, cesarean section is recommended. In the presence of fetal edema or oversized occupying lesions after 32 weeks of gestation, emergency cesarean section should be performed if vaginal delivery is difficult, and postnatal emergency surgery should be performed. antsaklis suggests early delivery and postnatal surgery for >32 weeks of gestation, while fetal intervention is appropriate for <32< span=""> weeks. Treatment Hormonal therapy Indications for hormonal therapy in CCAM: 1. high risk microcystic type in CCAM cases; 2. presence of fetal edema; 3. CVR>1.6. The possible mechanism of hormonal therapy is to address the immaturity of the lungs in CCAM cases: shunt puncture The drainage of the cyst (shunt puncture) first requires a visualization system to keep track of the mass and the puncture specific situation. A fetoscope is used to place the drainage tube between the thoracic cyst and the amniotic cavity under the guidance of the visualization system for treatment purposes. EXIT surgery (ex-utero intrapartum therapy, EXIT) EXIT surgery is performed at the time of birth, when the fetus is delivered by cesarean section but the umbilical cord is not broken, and the CCAM tumor is removed first, then the umbilical cord is broken to allow the newborn to start breathing in order to relieve the pressure of the mass on the chest cavity and relieve respiratory distress. Open fetal surgery The principles or goals of fetal surgery are: 1) to restore normal anatomy; 2) to restore normal physiology; and 3) to allow the lungs to grow and develop prior to birth. There are no clear indications for performing open fetal surgery in the fetal period. For asymptomatic or non-edematous CCAM with a CVR of 1.6 and significant compression or significant mediastinal shift, a tendency for edema or pre-existing edema, and excessive amniotic fluid, intervention in the fetal period, including open fetal surgery, is mostly required. Surgical options after birth The combination of other congenital anomalies in CCAM is rare, and most cases can be treated surgically after birth by normal delivery, and early surgical resection has become a generally accepted view. However, there is also a view that no further treatment is needed after birth (18% of all prenatal diagnoses). Those with definite symptoms after birth require emergency surgical treatment; there are no clear criteria for when to operate in asymptomatic cases. Surgery should be chosen at least 1 month after birth because, the risk of anesthesia begins to decrease gradually by the time the infant is 4 weeks old. Factors associated with the need for surgical resection are:the presence of significant respiratory symptoms, the risk of recurrent infection and mass malignancy; other clinical manifestations such as:coughing up blood, hemothorax, etc. However, there is an opinion that it is best not to wait until symptoms are present before surgery, as that has an impact on overall lung development. Summary Congenital lung lesions, most commonly CCAM, and intervention in severely involved fetuses (e.g., edema) can significantly alter perinatal survival rates. However, not much more is known about the outcome of short- or long-term lung development and neurological development, and a small number of cases have shown that congenital lung lesions increase neonatal morbidity, mainly preterm birth and respiratory distress at birth. prognosis is better in the absence of combined edema in CCAM and worse in the presence of edema. In fact, the need for fetal interventions is still a minority. There are no clear indications for open fetal surgery in the fetal period. Early intervention or even open fetal surgery is needed for CVR >1.6, with a clear mediastinal shift and a fetus with a tendency to have edema or with edema already present.