Abdominal Masses in the Newborn

The presence of an abdominal mass in the neonatal period is common, occurring in approximately 1 infant in 1000 live births fetal,period from birth to one month of age ultrasound has become technically refined and is more widely practiced. As a result, the presence of an abdominal mass in the fetus may be known long before birth,

Renal Masses in the Neonate Abdominal masses are frequent in newborn infants, two thirds being renal in origin. After thorough palpation of the abdomen, cystic masses must be differentiated from solid masses by ultrasound examination. The common benign cystic masses include: hydronephrosis, multicystic dysplasia, polycystic disease, and adrenal hemorrhage. Solid masses include: renal vein thrombosis, a renal ectopic kidney, or horseshoe kidneys. Occasionally, a renal mass may be malignant and correspond to congenital mesoblastic nephroma, Wilms’ tumor, or fetal hamartoma.

Neonatal renal tumours Neonatal renal tumours are rare, with only 7% of all neonatal tumours arising from the kidney. Presentation is usually as a flank mass or as a coincidental finding on either antenatal or postnatal ultrasound. Mesoblastic nephroma is the most common tumour to be found at this age, but Wilms' tumour and other malignant and benign tumours occur. Cross sectional imaging is useful to delineate the extent of the disease. Given the low malignant potential of these tumours, treatment is by radical nephroureterctomy, except in cases with bilateral disease or syndromic patients with a high incidence of metachronous tumours. Chemotherapy is rarely indicated. Survival is generally excellent for all tumour types in this age group, the exception being malignant rhabdoid tumour of the kidney which may have metastases at presentation.

Mesoblastic nephroma Mesoblastic nephroma is the most common renal tumor in neonates and infants and represents 3% of the pediatric renal tumors and accounts for approximately 54% of tumors in this age group. The mass may be first diagnosed when the detailed fetal anatomy scan is performed at 18-20 weeks' gestation. It was initially described as a benign tumor, but recent advances suggest that a spectrum of disease exists, with the classic type representing the benign disease and the cellular variant representing the aggressive disease, with the mixed tumors falling somewhere in the middle. Recent studies have indicated that the incidence of the cellular variant may be from 42-63%. Mesoblastic nephroma has a slight male predominance, with a male-to-female ratio of 1.5:1

Pathophysiology The classic and the cellular variants of mesoblastic nephroma differ in the age at presentation, histologic characteristics, imaging characteristics and the biologic behavior of the tumors. The classic variant presents earlier, usually before age 3 months. It usually presents as a solid mass with small foci of necrosis or hemorrhage. It does not invade the perinephric tissues or the vascular pedicle. It is associated with an excellent outcome after complete surgical resection of the tumor. On gross examination, the solid tumor is noncapsulated, with a whorled trabeculated appearance similar to leiomyomas, hence the name leiomyomatous hamartoma of the kidney. Histologically it consists of uniform spindle cells arranged in bundles with scattered foci of entrapped normal glomeruli and tubules.

Clinical details The diagnosis may be made antenatally on ultrasound. Polyhydramnios is reported in 71% of pregnancies associated with mesoblastic nephroma. The most common clinical presentation is an asymptomatic abdominal mass. Paraneoplastic syndromes such as hypertension or hypercalcemia may be present. Hypertension is thought to be secondary to increased renin production by the trapped glomeruli in the tumor.

Imaging findings Imaging findings can suggest the diagnosis prenatally or after birth, and they can be used to identify the organ of origin.. However, imaging results cannot be used to definitively differentiate a mesoblastic nephroma from a congenital Wilms tumor. Histologic examination is the only definitive test. Ultrasonography is widely available and routinely performed antenatally. However, it has the disadvantage of being the most operator-dependant modality. Margins of the tumor may not be accurately visualized, especially with large tumors. In cases of large tumors, the organ of origin may also not be definitively determined. MRI is being increasingly used as a prenatal diagnostic tool, but it is still considered experimental. Antenatal MRI examination may be limited by fetal motion and maternal discomfort. In addition, MRI may require sedation, as the typical exam times are longer. Intravenous contrast may be required to fully characterize the tumor.

Wilms' tumor Wilms' tumor (WT) may occur in newborn infants, but is more common in older children.The annual incidence of Wilms' tumor is eight per million under the age of 15years .the risk of developing this tumor is 1 in 10.000live births. Congenital Wilms' tumor is very rare indeed with an incidence of 0.16%of all cases of Wilms' tumor. This appears as a solid echogenic mass with a clearly defined capsule. Areas of hemorrhage and necrosis may be seen within the mass. The molecular genetics of WT involves one or more genes located on Chromosome #11 and probably other locations not yet elicidated. Germline mutations cause less than 5% of WTs; most WTs are sporadic. Precursor lesions to WT called nephrogenic rests may be detected before evolution to WT by imaging studies. several different syndromes are associated with nephrogenic rests and predisposition to WT.

Neonatal neuroblastoma. Neuroblastoma, an embryonal tumour arising from the sympathetic nervous system, is the most common neonatal malignancy accounting for >20% of neonatal cancers. Neonatal tumors—those occurring in the first 28 days of life—are rare. They comprise 2% of all paediatric malignancies, with an incidence of 1.58 to 3.65 per 100000 live births. It may present as an antenatal adrenal mass or more commonly with localised or metastatic (4s/Ms) disease, which is usually low risk with a very good clinical outcome.

Neonatal Neuroblastoma Patients with stage Ms disease without life- or organ-threatening symptoms or adverse genetic features (MYCN amplification or segmental chromosomal abnormalities) can be safely observed for spontaneous regression which may also occur with other localised neonatal neuroblastomas. Universal mass screening for neuroblastoma is not indicated but targeted screening of infants at risk of hereditary neuroblastoma with germline ALK or PHOX2B mutations is appropriate

Current Management of Neonatal Neuroblastoma Around 20% of neonatal neuroblastoma presents with spinal cord compression requiring prompt diagnosis and treatment with steroids and chemotherapy to relieve the cord compression. Infant under 3 months spontaneous regression of this tumor type, reduce therapy given to neonates with neuroblastoma and use a watch-and-wait.( Close observation ) Frequent assessment of respiratory status Avoidance of invasive surgical procedures intermediate-risk patients those life- or organ-threatening complication ,necessary very low dose radiation and chemotherapy

Fetal neuroblastoma In 90% of cases fetal neuroblastomas arise in the adrenal glands. They have been diagnosed as early as 19 weeks of gestation, but usually are seen in the third trimester (mean age of diagnosis 36 weeks)   In almost all cases the tumour undergoes maturation and regression, and prognosis is excellent with many institutions recommending conservative management 1. Ultrasound They are typically seen as a complex mass with cystic components (~50% 10) around the expected position of the fetal adrenal gland. Some lesions may appear entirely solid of predominantly cystic. Colour Doppler interrogation often shows diffuse vascularity rather than a single feeding vessel. Complications developmental of hydrops fetalis: uncommon but a concerning complication development of maternal pre-eclampsia

Frequency United States Neuroblastoma is the third most common pediatric cancer accounts for approximately 8% of childhood cancers in the United States. Approximately 650 new cases are diagnosed in the United States each year. Median age at diagnosis is 2 yr and 90% of cases are diagnosed by 5 yr of age . International Incidence in other industrialized nations appears to be similar to that observed in the United States. International reports have shown that the incidence rates of neuroblastoma are highest among high income countries in Europe and North America, and lower in low income countries in Africa, Asia, and Latin America. No published data are available on the incidence in the emerging high-income countries of Asia

Sacrococcygeal teratoma Sacrococcygeal teratoma (SCT) has an incidence of about 1/40,000 live births and is the commonest congenital tumour in the neonate . Altman classified SCT into 4 types based on the external component and intrapelvic/ intra-abdominal extension of the tumour (American Academy of Pediatrics Surgical Section classification) The SCTs seen at birth are usually Altman Type I and II (87%) Rarely Type III can also be seen in neonates .Type IV is typically seen later in life as there is no external component. Neonatal SCTs are usually benign with a good outcome after complete surgical excision with a low complication rate.

Sacrococcygeal teratoma mortality associated with prenatally diagnosed SCT is in the range of 30-50%,] and is attributed to tumor morphology and vascularity. Whereas some fetuses are born without complications, others can develop high-output cardiac failure, nonimmune hydrops fetalis and, ultimately, fetal demise. The vascular supply to an SCT commonly arises from the middle sacral artery, which can enlarge to the size of the common iliac artery and cause a vascular steal syndrome Polyhydramnios is commonly seen because of increased fetal cardiac output, which often leads to preterm labor and premature rupture of membranes. Conversely, oligohydramnios can also occur if an intrapelvic portion of the tumor causes significant urinary obstruction In severe cases, maternal mirror syndrome, in which the mother develops symptoms that mimic those of the hydropic fetus, may develop. Mothers develop symptoms similar to those of severe preeclampsia, such as hypertension, emesis, peripheral edema, pulmonary edema, and proteinuria.

Sacrococcygeal teratoma Patients in whom SCT is diagnosed postnatally typically do well after early surgical resection, and the main cause of mortality in these patients (though rare) is attributed to malignancy

Sacrococcygeal Teratoma (SCT)

Sacrococcygeal Teratoma (SCT)

Sacrococcygeal Teratoma (SCT)