atypical teratoid / rhabdoid tumors ( at / rts ) of the central nervous system ( cns ) are rare and high - grade malignant neoplasms frequently seen in children below the age of 3 years . their diagnosis is based on the immunohistochemical study , and their prognosis is usually dismal . they have been frequently reported in the posterior fossa , but they can occur anywhere in the cns . we report the fifth case of lateral ventricle at / rt in a 2-month - old baby with the particularity of good long - term outcome after radical surgery and intensive chemotherapy . a 2-month - old male baby with normal perinatal history presented with rapid increasing of his head circumference attaining 43 cm on 1 month . contrast - enhanced brain computed tomography ( ct ) scan showed a well - delimited large heterogeneous mass in the left lateral ventricle . magnetic resonance imaging ( mri ) revealed a huge heterogeneous mass with solid and cystic components in the posterior part of the body of the left lateral ventricle compressing the parieto - occipital brain parenchyma with associated peritumoral edema . the solid component was slightly hyperintense on t1 , hypointense on t2 , and markedly enhanced after contrast administration [ figure 1a  c ] . ( a ) axial t1-weighted image : solid and cystic lesion in the left lateral ventricle extended to the parieto - occipital parenchyma . ( c ) sagittal t2-weighted image : hyperintense cystic components with important peritumoral edema the two lateral ventricles are moderately dilated . the solid component was pink , firm , highly vascular and attached to choroid plexus with a large feeding artery , which was clipped allowing complete removal of the total mass without bleeding . postoperative brain ct scan confirms complete removal of the tumor , and the patient was discharged 10 days after surgery . histopathological examination of the mass depicted the aggregation of large , pale , and polygonal cells with distinct cell border , abundant cytoplasm , and eccentric vesicular nuclei with prominent nucleoli and showed mesenchymal and epithelial components [ figure 2 ] . photomicrograph of the tumor specimens showing a variety of histologic patterns with areas of rhabdoid cells and epithelial components ( h and e , 200 ) immunohistochemical study revealed tumor cells strongly positive to vimentin , epithelial membrane antigen , smooth muscle actin , and synaptophysin , and focally positive to glial fibrillary acidic protein . it also demonstrated a lack of nuclear integrase interactor 1 ( ini-1 ) in tumor cells . control brain ct scan , 3 years and a half after surgery , showed no recurrence [ figure 3 ] . at / rts tumors are rare and highly malignant embryonal cns neoplasms , they have been increasingly described since their definition as an entity in 1996 . they were introduced to the world health organization brain tumor classification and international classification of diseases for oncology ( third edition ) in 2000 . their exact pathogenesis is unknown , but some of their histological features are similar to those of malignant rt of the kidney and soft tissue . they are always sporadic , but they can occur as a part of rt predisposition syndrome . they have been predominantly observed in very young children usually less than 3 years of age with a prevalence estimated between 1% and 2% among all pediatric cns tumors . are commonly located in the posterior fossa , but they can occur anywhere in the cns . 4 cases within the lateral ventricle were reported in the literature , and only 2 are well - documented . nonspecific symptoms and signs such as lethargy , irritability , vomiting , macrocephaly , and seizures are frequent in children younger than 3 years of age . our patient presented with macrocephaly , whereas donovan et al . described a case in a 3-month - old female revealed by seizures . imaging features of at / rt are usually nonspecific , although large infratentorial tumor with signs of bleeding and meningeal dissemination is highly suggestive . on ct scan , the tumor shows an iso- or hyper - dense solid part altering with cystic and necrotic hypodense areas with occasional hyperdensity due to calcification or hemorrhage . after contrast administration , the solid part shows marked enhancement . on mri , the solid component is usually iso or hypointense on t1-weighted sequence and iso or hyperintense on t2-weighted sequence and strongly enhanced after gadolinium administration with moderate to marked surrounding edema . the complete or partial rim enhancement of the cystic or necrotic area , published in several reports , is considered as a typical pattern . however , it does not seem to be specific , but it could help in the differential diagnosis of cns tumors in young children . radiological feature of at / rt is similar to those of primitive neuroectodermal tumor ( pnet)/medulloblastoma , ependymoma , choroid plexus papilloma or carcinoma , and teratoma . in addition , some renal rts are associated with synchronous at / rt and with other intracranial neoplasms such as pinealoblastoma , medulloblastoma , or pnet . the earlier age of onset , polymorphic appearance , larger size , and variability of location help in differentiating at / rt from other tumors . the tumor was composed of rhabdoid cells and undifferentiated small cells mixed with epithelial or mesenchymal components or mimicking pnet / medulloblastoma . they are described as large , pale cells with oval , polygonal or elongated nuclei , and eosinophilic or pale cytoplasm . vimentin , epithelial membrane antigen , cytokeratin , smooth muscle actin , glial fibrillary acid protein , s100 , and synaptophysin were positive in varying proportions , whereas desmin and ini-1 were usually negative . at / rt are almost always associated with a mutation in the tumor suppressor gene rsnfs / ini-1 ( known as smarcb1 ) on chromosome 22q11.2 locus which are absent in medulloblastoma and pnet tumors but may be present in other tumors such as choroid plexus carcinoma . the presence of mesenchymal and neuronal marker and the absence of papillary structures are helpful for the diagnosis . high dose of chemotherapy is active against at / rt and may be associated with a high chance of cure but must be approached with caution due to its potential toxicity . radiotherapy is classically delayed for young children under 3 years due to its neurotoxicity such as cognitive , motor , visual , and hearing impairment , but some authors recommend immediate postoperative focal irradiation particularly for children without metastatic disease . despite aggressive treatment , the outcome is very poor especially in very young children . our patient is alive after 3 years and half of follow - up without neurological deficit or recurrence on control ct scan . at / rt should be kept in mind in the differential diagnosis of a large tumor of the lateral ventricle , particularly in young children . long - term survival can be seen with early diagnosis , radical surgery , and intensive chemotherapy .
atypical teratoid / rhabdoid tumors ( at / rts ) are rare and highly malignant embryonal central nervous system neoplasms , usually seen in very young children with rapid fatal outcome despite aggressive treatment . 
 they are most commonly located in the posterior fossa . 
 intraventricular location is extremely rare . to the best of our knowledge , 
 only 4 cases of lateral ventricle location were reported in the literature . 
 we report the fifth case of lateral ventricle at / rt in a 2-month - old male who presented with rapid increase of his head circumference . 
 brain computed tomography scan and magnetic resonance imaging showed heterogeneous huge mass within the left lateral ventricle extending to the parieto - occipital parenchyma and markedly enhancing by contrast . 
 the baby underwent left transparietal approach with complete removal of the tumor . 
 histological examination confirmed the diagnosis of at / rt . 
 an aggressive chemotherapy was administrated postoperatively . 
 the outcome is good without neurological deficit or recurrence after 3 years and half of follow - up .