Atypical teratoid rhabdoid tumor of the lateral ventricle.

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.

Introduction

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.[1]

Their diagnosis is based on the immunohistochemical study, and their prognosis is usually dismal.[12]

They have been frequently reported in the posterior fossa, but they can occur anywhere in the CNS. Lateral ventricle location is extremely rare.[3] It has only been reported in 4 cases in the literature.

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.

Case Report

A 2-month-old male baby with normal perinatal history presented with rapid increasing of his head circumference attaining 43 cm on 1 month.

Neurological and general examinations were normal.

The laboratory examinations were within normal limits.

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].

Figure 1

Preoperative magnetic resonance imaging. (a) Axial T1-weighted image: solid and cystic lesion in the left lateral ventricle extended to the parieto-occipital parenchyma. (b) Axial T1-weighted postgadolinium image: Intense tumor enhancement. (c) Sagittal T2-weighted image: Hyperintense cystic components with important peritumoral edema

The two lateral ventricles are moderately dilated.

The baby underwent a left transparietal approach with total removal of the tumor.

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.

The postoperative course was uneventful; the child was conscious without neurological deficit.

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].

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.

These finding confirmed the diagnosis of AT/RT.

Spine MRI and thoracoabdominal CT scan were normal.

The child received intensive chemotherapy for 1 year according to BBSFOP protocol.

The outcome is good with normal developmental milestones and without complications.

Control brain CT scan, 3 years and a half after surgery, showed no recurrence [Figure 3].

Figure 3

Three years and half postoperative contrast-enhanced computed tomography scan showing no tumor recurrence

Discussion

AT/RTs tumors are rare and highly malignant embryonal CNS neoplasms, they have been increasingly described since their definition as an entity in 1996.[12]

They were introduced to the World Health Organization brain tumor classification and International Classification of Diseases for oncology (third edition) in 2000.[1]

Their exact pathogenesis is unknown, but some of their histological features are similar to those of malignant RT of the kidney and soft tissue.[2]

They are always sporadic, but they can occur as a part of RT predisposition syndrome.[12]

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. Male predominance was frequently reported.[123]

AT/RTs are commonly located in the posterior fossa, but they can occur anywhere in the CNS. Intraventricular location is very rare.[34]

To the best of our knowledge, 4 cases within the lateral ventricle were reported in the literature,[3456] and only 2 are well-documented.[34]

Clinical signs of raised intracranial pressure are the most common features of such location. 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.[3]

Imaging features of AT/RT are usually nonspecific, although large infratentorial tumor with signs of bleeding and meningeal dissemination is highly suggestive.[6]

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.[67]

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. Cystic and necrotic areas are usually seen, whereas hemorrhagic changes are occasionally found.[6]

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.[7]

Radiological feature of AT/RT is similar to those of primitive neuroectodermal tumor (PNET)/medulloblastoma, ependymoma, choroid plexus papilloma or carcinoma, and teratoma.[67]

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.

Histopathologically, AT/RTs are classified as WHO grade IV neoplasms. The tumor was composed of rhabdoid cells and undifferentiated small cells mixed with epithelial or mesenchymal components or mimicking PNET/medulloblastoma.[1258]

Rhabdoid cells are considered as the histological hallmark of AT/RT. They are described as large, pale cells with oval, polygonal or elongated nuclei, and eosinophilic or pale cytoplasm. The nuclei have open chromatin pattern and small to moderately prominent nucleolus.[58]

Immunohistochemical examination is essential for distinguishing AT/RT from PNET/medulloblastoma. 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.[258]

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.[28]

Treatment is now focusing on radical surgery followed by aggressive chemotherapy and radiotherapy.

Maximal safe surgical resection should be attempted.[910]

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.[9]

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.[10]

Despite aggressive treatment, the outcome is very poor especially in very young children. Most patients succumb to their disease within 1 year of local recurrence.[1910]

Our patient is alive after 3 years and half of follow-up without neurological deficit or recurrence on control CT scan.

Conclusion

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.

Financial support and sponsorship

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Conflicts of interest

There are no conflicts of interest