A 32-year-old gravida 1, para 0 woman was referred to our maternal fetal care center at 35 weeks’ gestation for a new finding of bilateral ventriculomegaly. The pregnancy had been uncomplicated and prenatal laboratory testing was unremarkable. Maternal medications included prenatal vitamins, with loratadine, acetaminophen, and lorazepam as needed. Maternal and family history did not include any severe neonatal or childhood conditions. Cell-free fetal DNA screening did not detect aneuploidy. Findings of fetal anatomic survey were normal at 20 weeks’ gestation, and follow-up ultrasonography to assess cord insertion showed only marginal cord insertion diagnosed at 32 weeks’ gestation. Fetal ultrasonography performed at 35 weeks’ gestation for evaluation of fetal growth demonstrated a new finding of bilateral ventriculomegaly with dilation of the third ventricle, concerning for aqueductal stenosis (Fig 1A).A multidisciplinary team reviewed the prenatal records and performed both fetal ultrasonography and magnetic resonance imaging (MRI) at 36 4/7 weeks’ gestation. Fetal MRI revealed an unexpected finding of a large heterogeneous soft tissue mass centered within the fetal right hemipelvis and groin (Fig 1B). Fetal ultrasonography confirmed a large echogenic and hypervascular soft tissue mass in the right hemipelvis (Fig 1C), which extended into the anterior compartment of the right thigh via the inguinal canal, and into the right hemiscrotum, with associated bilateral scrotal edema. MRI also confirmed moderate to severe lateral and third ventriculomegaly and identified a 6-mm nodule in the inferior margin of the cerebral aqueduct. Additional findings included a 1.3-cm area of signal abnormality in the right hepatic dome and a nodular area of spinal canal effacement in the lower thoracic spine.Our multidisciplinary team included clinicians from maternal-fetal medicine, neonatology, pediatric oncology, and social work. The team met with the family, interpreted imaging findings, and discussed the prenatal differential diagnosis. The pediatric oncology clinicians counseled the couple that these imaging findings of pelvic and cerebral aqueductal masses were concerning for malignancy (the primary lesion was unknown), with potential areas concerning for metastatic dissemination to the liver and spinal canal. The family was informed that definitive diagnosis of the disease process would require postnatal tissue characterization, and that the diagnosis would provide information relevant to prognosis and therapy options.Together the team developed a comprehensive care plan, including delivery planning, postnatal evaluation, and possible intervention. The decision was made to induce labor as soon as possible to facilitate diagnosis and treatment, given that the gestational age was more than 36 weeks. Concerns associated with waiting for spontaneous labor included the risk of continued growth of these masses, possibly leading to significant organ dysfunction and potentially death. Cesarean delivery was not believed to offer fetal benefit as there was no evidence of cervical spine involvement, and head and abdominal circumferences were appropriate despite known ventriculomegaly and tumor involvement. The postnatal plan included admission to a level IV NICU with immediate access to craniospinal and body MRI-guided biopsy, and pediatric oncology and pediatric neurosurgery.At 36 6/7 weeks’ gestation, a male infant weighing 3,340 g (83rd percentile) was delivered via induced vaginal delivery. His Apgar scores were 8 (-2 color) and 9 (-1 color) at 1 and 5 minutes, respectively. He received routine delivery room resuscitation including timed cord clamping for 30 seconds. Cord blood was collected at the time of delivery and sent for oncologic next-generation sequencing assay. Physical examination at the time of birth was notable for a nonbulging, open, soft, and flat anterior fontanelle, head circumference 35 cm (88th percentile) and a palpable right hemipelvic mass extending into the inguinal region and groin, with an erythematous projection from the left scrotum.The infant was admitted to the NICU for diagnostic evaluation and treatment of a presumed neonatal solid tumor with metastatic involvement. Postnatal MRI of the abdomen and pelvis demonstrated a large hypervascular soft tissue mass centered in the right side of the pelvis, encasing the right psoas muscle and extending into the upper thigh via the inguinal canal, with extension into the mid-abdomen (Fig 2A, 2B). The right iliac veins and arteries were encased and compressed by the mass. Intraspinal extension was noted at the T10 level with spinal cord displacement and liver metastases including a large 3.5-cm soft tissue mass within the liver (Fig 2C). Metastatic lesions also were seen in the left gluteal and paraspinal muscles at the T11 level. Scrotal ultrasonography showed the heterogeneous mass in the right groin (Fig 2D); the testes and kidneys appeared sonographically normal.Head ultrasound findings were remarkable for moderate to severe supratentorial ventriculomegaly involving the lateral and third ventricles with elevated resistive index within the anterior cerebral artery, suggesting increased intracranial pressure. Brain MRI confirmed the ultrasound findings of obstructive hydrocephalus (Fig 3A), in addition to a tectal mass causing ventral occlusion of the cerebral aqueduct and dorsal projection into the quadrigeminal cistern and tentorial incisura (Fig 3B). The mass was noted to have hemorrhaged since the most recent prenatal imaging, resulting in multiple small locules with hematocrit levels and edema in the surrounding dorsal brainstem. Spine MRI noted an intradural extramedullary plaque of enhancement at right dorsal C2, concerning for leptomeningeal tumor dissemination. The paraspinal tumor extended through the right T12-L1 neural foramen and intruded upon the right lateral epidural space (Fig 3C). Multiple additional paraspinal soft tissue deposits were noted in the posterior neck and lower back concerning for metastases.On postnatal day 2, the patient underwent central catheter placement and core needle biopsy of the right groin mass by interventional radiology. The biopsy showed a poorly differentiated high-grade malignant tumor with large round vesicular nuclei and prominent nucleoli. There was also evidence of necrosis, calcification, and occasional rhabdoid inclusions. INI1 (protein product of SMARCB1) immunohistochemistry was inconclusive (no definitive and consistent loss across cells). Molecular analysis of the tumor identified a biallelic deletion in SMARCB1 at 22q11.23, which confirmed the diagnosis of malignant rhabdoid tumor (MRT). Eventually, further genetic testing confirmed a germline SMARCB1 mutation in this patient.Pediatric oncology counseled the family that based on the extent of the tumor and its aggressive features, it was likely to carry a very poor prognosis with limited likelihood of cure. While considering treatment options, the family voiced a preference for therapies that could mitigate tumor progression and give them more time with their son despite the likely poor prognosis. The family was counseled extensively about the side effects of chemotherapy and provided informed consent.On postnatal day 4, the patient was initiated on a vincristine, doxorubicin, and cyclophosphamide (VDC) regimen, dosed at 50% due to his extremely young age. The patient remained stable in room air and with ad lib feeding, with no neurologic deficits. Findings of his baseline cardiac evaluation and biochemical laboratory testing were normal. He was started on ondansetron and dexamethasone as an antiemetic, omeprazole for gastrointestinal protection, dexrazoxane for cardiac protection, mesna for uroprotection, sulfamethoxazole-trimethoprim for Pneumocystis jirovecii pneumonia prophylaxis, and filgrastim for neutrophil recovery. He also received hyperhydration with intravenous fluids during initiation.Approximately 2 weeks after initiation of chemotherapy, in the setting of neutropenia and mucositis, the patient developed feeding intolerance requiring nasogastric feedings, which progressed to hematemesis and bloody stools. Abdominal imaging showed gastric pneumatosis concerning for neutropenic enterocolitis (Fig 4A). The patient experienced clinical decompensation requiring intubation, but was successfully extubated a few days later. He was treated with 14 days of bowel rest and broad-spectrum antibiotics, following which he was restarted on enteral feedings, which he tolerated without complication. His last dose of vincristine was held in the setting of his gastrointestinal issues. Pediatric surgery was consulted but there was no indication for surgical intervention; the patient improved with medical therapy alone.Pediatric neurosurgery was consulted postnatally regarding obstructive hydrocephalus secondary to the tectal brain mass, which was diagnosed as a synchronous atypical teratoid rhabdoid tumor (ATRT). Neurosurgery recommended close monitoring of the infant’s neurologic status, head circumference measurements, and serial head ultrasonography, all of which initially remained stable. His repeat MRI at 1 month of age showed worsening obstructive hydrocephalus with concern for increased tumor size. Given these concerns, the patient underwent an endoscopic third ventriculostomy with choroid plexus cauterization and Rickham reservoir placement. Follow-up MRI after the procedure showed improved ventriculomegaly but an increase in the size of the tumor within the aqueduct. Our institution’s typical approach to rhabdoid tumor consists of alternating chemotherapy cycles of VDC and ifosfamide, carboplatin, and etoposide (ICE). ICE was felt to have superior central nervous system (CNS) penetration compared with VDC, so the patient proceeded with a reduced-dose cycle of ICE chemotherapy, which he completed successfully. After 2 cycles of chemotherapy, his restaging scans showed slight improvement of peripheral tumor burden but progression of his CNS disease. Given progressive CNS disease, the patient was transitioned to a chemotherapy regimen based on the Head Start II protocol for pediatric brain tumors (cisplatin, etoposide, cyclophosphamide, vincristine, and high-dose methotrexate) plus intrathecal topotecan. He underwent 3 full cycles of chemotherapy with this regimen.His course was complicated by feeding intolerance that was initially attributed to chemotherapy-associated nausea and baseline increased intracranial pressure. Given the persistence and projectile emesis, an abdominal radiograph and ultrasound scan were obtained, which were notable for pyloric thickening without significant opening of the pyloric channel, consistent with pyloric stenosis (Fig 4B). The patient underwent an uncomplicated laparoscopic pyloromyotomy and was able to quickly return to full oral feedings and resume chemotherapy.After 5 cycles of intensive induction chemotherapy, his CNS and intra-abdominal disease remained stable, with no new lesions noted. However, prognosis for an aggressive malignancy without a feasible local control option remained poor. He was not considered a candidate for CNS radiation or autologous stem cell transplantation due to his young age. After careful consideration, his parents opted to transition to a maintenance chemotherapy regimen; he was discharged at 50 days after birth but required multiple readmissions for each chemotherapy course. At 7 months of age, he transitioned to outpatient-only treatment with a modified antiangiogenic metronomic oral chemotherapy regimen and continued intrathecal topotecan administration. Palliative care worked closely with the family to help with symptom management and goals of care planning.Following 2 cycles of maintenance chemotherapy, his parents noted a new right groin mass that appeared to be growing rapidly and he was emergently admitted. Repeat MRI of the brain, spine, abdomen, pelvis, and lower extremities demonstrated marked progression of disease including increased size of all previous residual sites of disease as well as multifocal new sites of disease in the pleura, abdomen, right lower extremity, bilateral inguinal canals, and brain. He received 1 cycle of immunotherapy on a clinical trial protocol with the checkpoint inhibitors ipilimumab and nivolumab. However, his disease continued to progress clinically. Based on these findings, he was removed from protocol therapy, transitioned to comfort care, and died shortly thereafter.We present a rare case of a prenatally diagnosed malignant solid tumor, an MRT with synchronous ATRT, and the obstetric, neonatology, and oncologic considerations in the management of this neonatal malignancy. The delivery of a fetus with multiple anomalies such as soft tissue tumors and hydrocephalus requires careful consideration of fetal and maternal risks, as well as coordination with multiple teams, including obstetricians, neonatologists, and appropriate pediatric subspecialists.Timing of delivery is the first crucial decision for patients with a tumor, when teams need to balance the fetal and maternal risks of complication with continued pregnancy near term against the risks and benefits of early delivery. (1) With continued pregnancy, there is a risk of progression of both tumor and obstructive hydrocephalus (if cerebral tumor). Some fetal tumors can be managed without recommendation for early delivery, however, aggressive tumors may warrant earlier timing of delivery due to life-threatening risks to the fetus. (1) In cases of hydrocephalus with macrocephaly (head circumference >98th percentile), there may be a benefit to delivery in the early-term period (37–38 weeks’ gestation) due to the theoretical risk of worsening cerebral cortical compression and damage. (1)(2)Subsequently, consideration for method of delivery is often tailored to the specific anomaly and its severity. In general, spontaneous labor and vaginal delivery carries the lowest risk for maternal morbidity. Cesarean section can be considered if there are concerns for airway obstruction, the need for immediate neonatal surgical intervention, or if the size or nature of the mass presents challenges to vaginal delivery, such as cephalopelvic disproportion or shoulder/abdominal dystocia. (1)(2) In the case of hydrocephalus without macrocephaly, route of delivery does not significantly affect neonatal outcomes and therefore, vaginal delivery is typically recommended. (2) For intra-abdominal solid masses, abdominal dystocia may occur if abdominal girth is enlarged (abdominal circumference of >2 standard deviations above the mean for term infants) and elective cesarean section may be considered. (2)Neonates with soft tissue tumors and hydrocephalus may require no more than routine resuscitative measures. (3) However, if the location and size of the soft tissue tumor results in airway obstruction, advanced airway management would be needed at delivery, and in some cases of critical airways, the presence of pediatric otolaryngology at delivery. Similarly in the case of severe hydrocephalus, teams should be prepared for airway management due to the risk of apnea and hypoventilation.Prenatal diagnosis of malignancy is rare; neonatal tumors comprise only about 2% of pediatric cancers, with a reported incidence of 1 in every 27,000 to 33,500 live births. (4)(5) Many masses identified in the neonatal period are benign. Of neonatal malignancies, the most common types are germ cell tumors (mainly teratomas) and neuroblastoma, followed by soft tissue sarcomas and renal tumors (most commonly congenital mesoblastic nephroma). (4) MRT is an extremely rare and aggressive embryonal malignancy primarily seen in infants, with an average age at diagnosis of 12 months. (6) Annual US incidence of MRTs is less than 1 per million. MRTs arise predominantly in the brain (referred to as ATRT), kidney, and other extrarenal soft tissues such as the skin, liver, and lung, though it has been reported in almost all soft tissues. (7)In epidemiologic analyses, more than half of fetal and neonatal cases of MRT have metastatic disease at diagnosis, and the presence of CNS disease has a significant adverse impact on survival. (6)(8) This was all consistent with our patient’s presentation and eventual clinical course. Interestingly, there have also been a few case reports of fetal MRTs with evidence of placental metastases but without evidence of maternal disease. (9)(10)(11) In our case, maternal placental pathology was normal, without evidence of metastasis.The pathophysiology of MRTs is related to a hallmark genetic abnormality, biallelic deletion, or inactivating mutation of the SMARCB1 gene. SMARCB1 is an epigenetic tumor suppressor gene located on chromosome 22q11.2. (12) Germline mutation of 1 copy of SMARCB1 is known as rhabdoid tumor predisposition syndrome (RTPS) and is associated with an increased risk of MRT development. (13)(14)(15) Our patient did have a SMARCB1 germline mutation; however, there was no family history of MRTs. Both parents underwent genetic testing, the result of which was negative for SMARCB1 alterations, suggesting a de novo deletion rather than an inherited one. The family received genetic counseling regarding the implications for siblings and future offspring; risk of RTPS for future offspring was felt to be very low, potentially nonzero due to the risk of gonadal mosaicism.Treatment for rhabdoid tumors may include surgery, chemotherapy, radiation therapy, or high-dose chemotherapy with autologous stem cell rescue. Treatment of MRT can be challenging in infants, as age precludes various forms of therapy. For example, cranial radiation therapy is precluded due to its adverse neurocognitive effects, and there are technical challenges with collecting stem cells from infants due to their low body weight. As in our patient’s case, chemotherapy regimens may need to be dose-reduced for neonatal patients given the altered pharmacokinetics for this age group.Regardless of the MRT’s location, these malignancies have a poor prognosis, with overall 5-year survival of 33% and median survival of less than 1 year. Age at diagnosis of less than 2 years or more than 18 years and disseminated disease are associated with worse outcomes. (16)(17) A recent literature review of pediatric cases of MRTs with synchronous or metachronous ATRT revealed that the median survival was 6 months from presentation and almost all patients died of their disease, (18) which is consistent with our case as well.As our patient underwent intensive chemotherapy treatment in the NICU, he received supportive management of chemotherapy-induced nausea and vomiting. Collaboration with our hospital’s neonatal and oncology pharmacists was helpful in determining which antinausea medications could be safely given at this age. Ultimately, the patient was treated with ondansetron, dexamethasone, and metoclopramide with good control of nausea and was able to continue feeding by mouth through therapy.This patient also developed neutropenic enterocolitis (typhlitis), a gastrointestinal complication of chemotherapy. Neutropenic enterocolitis is an inflammatory bowel disease that typically affects severely neutropenic patients, defined as an absolute neutrophil count of less than 500 cells/μL. (19) This clinical entity was first described in pediatric patients with leukemia, but has subsequently been reported in adult oncologic patients as well as other immunosuppressed patients. (20)(21)(22) Timing of onset typically coincides with the nadir of neutropenia. (23) The pathogenesis of neutropenic enterocolitis is poorly understood; however, it appears to occur with intestinal mucosal injury in the setting of immunosuppression, resulting in intestinal edema and a disrupted mucosal surface that becomes susceptible to bacterial intramural invasion. (24) Chemotherapy agents can also cause direct mucosal injury and alter gut motility. (25) Patients can present with abdominal pain, distention, diarrhea, fever, nausea, vomiting, and rarely, melena or hematochezia. (20) Diagnosis often requires imaging given the nonspecific symptoms; computed tomography is the preferred modality over plain film radiography, due to higher accuracy. (26)(27) Characteristic findings include bowel wall thickening, mesenteric stranding, bowel dilation, and pneumatosis. (27) Notable complications of neutropenic enterocolitis include bowel perforation and severe hemorrhage, which may require surgical intervention and transfusion support. In our case, the patient presented with feeding intolerance during a period of neutropenia and was found to have gastric pneumatosis and portal venous gas on imaging. Our patient was treated as a case of uncomplicated neutropenic enterocolitis with bowel rest and broad-spectrum antibiotics.Our patient was also diagnosed with pyloric stenosis around 2 months of age, which is the typical age at presentation. The incidence is notably high in the western world and estimated to be 2 to 5 per 1,000 live births. (28) Pyloric stenosis is characterized by the gradual hypertrophy of the pylorus resulting in obstruction and presenting with persistent emesis after feeding. Risk factors for pyloric stenosis relevant to this patient include male sex and white Northern European ancestry. (28) Other known risk factors include maternal smoking during pregnancy and macrolide use early in life. (28) Based on our review of the literature, there have been no reports of associations among chemotherapy, malignancy, and pyloric stenosis, which leads us to believe that this diagnosis was a coincidence in our patient’s case.In conclusion, neonatal malignant tumors represent only 2% of all childhood malignancies and are more likely to have a genetic etiology. (29) More neonatal tumors are now being diagnosed prenatally, due to the increasing use of prenatal ultrasonography; however, exact diagnosis requires tissue biopsy, which makes prognostication and prenatal counseling challenging. MRTs represent a very rare type of malignant solid tumor that presents in infancy and carries an extremely poor prognosis. Multidisciplinary care is essential when caring for patients with a neonatal malignancy, with key input from obstetrics, neonatology, oncology, genetics, neurosurgery, general surgery, pharmacy, social work, and palliative care throughout the patient’s treatment course.MRTs are extremely rare and aggressive soft tissue malignancies that can occur anywhere in the body and generally present in the first year of age.Diagnosis in infancy and presence of metastatic disease are associated with poor outcome for MRT, with median survival being less than 1 year.SMARCB1 is an epigenetic tumor suppressor gene involved in chromatin remodeling, and biallelic SMARCB1 mutations are the characteristic genetic abnormalities of MRTs.Treatment of MRTs can include chemotherapy, radiation therapy, surgery, or autologous stem cell transplantation.Treatment of neonatal patients with MRT and/or ATRT is particularly challenging due to the developing brain’s susceptibility to toxicity as well as other technical limitations.Neutropenic enterocolitis is a life-threatening gastrointestinal complication that occurs most frequently in the setting of intensive chemotherapy in oncologic patients.Multidisciplinary care is essential when caring for patients with neonatal malignancy, including obstetrics, neonatology, oncology, genetics, general surgery, neurosurgery, pharmacy, social work, and palliative care.Hypertriglyceridemia in Preterm Infants 1. B; 2. C; 3. A; 4. E; 5. CPostdischarge Nutrition in Preterm Infants 1. A; 2. C; 3. D; 4. E; 5. B