A case of congenital supratentorial tumor: Atypical teratoid/rhabdoid tumor or primitive neuroectodermal tumor?

Two embryonal CNS tumors, atypical teratoid/rabdoid tumor (AT/RT) and primitive neuroectodermal tumor (PNET), may be confused with each other and misdiagnosed. Here we report an infant with a congenital supratentorial tumor, which was detected by fetal MRI at 37 weeks gestation. On routine histological examination, the tumor was composed mainly of small undifferentiated cells, among which many rhabdoid cells and occasional sickle‐shaped embracing cells were observed. No mesenchymal or epithelial areas were evident. Our impression was that the tumor was an atypical example of AT/RT. Immunohistochemically, almost all the tumor cells were strongly positive for vimentin. However, epithelial membrane antigen was notably negative, and most of the tumor cell nuclei were clearly positive for INI1. In addition, many tumor cells were positive for neurofilament protein. There were also occasional small areas containing many tumor cells positive for glial fibrillary acidic protein. Finally, a diagnosis of PNET, with a rhabdoid phenotype and expression of neuronal and glial markers, was made. In the present case, application of INI1 immunostaining was very helpful for distinguishing PNET from AT/RT.     

Rhabdoid tumor predisposition syndrome with renal tumor 10 years after brain tumor

We report a case of rhabdoid tumor predisposition syndrome with a renal tumor developing 10 years after a brain tumor, which demonstrated an unexpectedly favorable outcome. A 2-year-old boy underwent gross total resection of a brain tumor located in the fourth ventricle, and received adjuvant chemotherapy and radiotherapy. At the age of 11 years, a renal tumor was found and nephrectomy was performed. He is currently alive without evidence of disease over 2 years without postoperative therapy. Histologically, rhabdoid cells were observed in both brain and renal tumors. Loss of SMARCB1 (also known as INI1) expression was found in the nucleus of both tumor cells. Genetic testing revealed pathogenic variants of SMARCB1 exon 5 in the renal tumor and SMARCB1 exon 9 in the brain tumor. In addition, heterozygous deletion of 22q11.21-q11.23 containing the SMARCB1 locus was shared by both tumors and this deletion was identified in normal peripheral blood. Considering the histopathological and genetic findings, our case was considered to be rhabdoid tumor predisposition syndrome with atypical teratoid/rhabdoid tumor and late-onset rhabdoid tumor of the kidney.     

Atypical teratoid/rhabdoid tumor arising in pleomorphic xanthoastrocytoma: A case report

Atypical teratoid/rhabdoid tumor (AT/RT) is a rare, highly malignant, true rhabdoid tumor in the central nervous system predominantly presenting in young children. AT/RT typically shows rhabdoid cells which can also be seen in other tumors, but it is differentiated from other tumors by the specific genetic alteration involving the SMARCB1 gene. Only a few cases of AT/RT arising in low‐grade glioma have been reported. A 13‐year‐old girl presented with headache, dizziness, nausea and vomiting. A 4.7 cm cerebellar mass was found on MRI. The mass was totally removed. Histologically, the tumor revealed two distinct morphologic appearances: central areas of AT/RT containing rhabdoid cells and sarcomatous component in the background of pleomorphic xanthoastrocytoma (PXA). Immunohistochemically, PXA areas retained nuclear expression of INI‐1 and low Ki‐67 proliferation index, whereas AT/RT component showed loss of INI‐1 nuclear expression and markedly elevated Ki‐67 proliferation index. Epithelial membrane antigen (EMA), smooth muscle actin (SMA), and p53 protein were positive only in AT/RT. BRAF V600E mutation was identified in PXA by real‐time polymerase chain reaction. We report a rare case of AT/RT arising in PXA which is supposed to progress by inactivation of INI‐1 in a pre‐existing PXA.     

Advances in the molecular classification of pediatric brain tumors: a guide to the galaxy

Central nervous system (CNS) tumors are the most common solid tumor in pediatrics, accounting for approximately 25% of all childhood cancers, and the second most common pediatric malignancy after leukemia. CNS tumors can be associated with significant morbidity, even those classified as low grade. Mortality from CNS tumors is disproportionately high compared to other childhood malignancies, although surgery, radiation, and chemotherapy have improved outcomes in these patients over the last few decades. Current therapeutic strategies lead to a high risk of side effects, especially in young children. Pediatric brain tumor survivors have unique sequelae compared to age-matched patients who survived other malignancies. They are at greater risk of significant impairment in cognitive, neurological, endocrine, social, and emotional domains, depending on the location and type of the CNS tumor. Next-generation genomics have shed light on the broad molecular heterogeneity of pediatric brain tumors and have identified important genes and signaling pathways that serve to drive tumor proliferation. This insight has impacted the research field by providing potential therapeutic targets for these diseases. In this review, we highlight recent progress in understanding the molecular basis of common pediatric brain tumors, specifically low-grade glioma, high-grade glioma, ependymoma, embryonal tumors, and atypical teratoid/rhabdoid tumor (ATRT). © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Teratoid Wilms' Tumor: Report of a Unilateral Case

A unilateral teratoid Wilms' tumor was removed 2.5 weeks after the institution of chemotherapy. Teratoid Wilms' tumor is an extremely rare renal tumor, and only four cases, all bilateral, have been reported. Because of the finding of deep cortical intralobar nephroblastomatosis, strongly associated with bilateral Wilms' tumors, the patient has been closely followed since surgery without evidence of tumor in the remaining kidney at 2 years.     

Central nervous system atypical teratoid/rhabdoid tumors of infancy and childhood

Summary Clinical and morphological features of an apparently unique, biologically aggressive central nervous system tumor in 32 infants and children are presented. This neoplasm is formed wholly or partly by rhabdoid cells, areas resembling typical primitive neuroectodermal tumor, and, less frequently, malignant mesenchymal and/ or epithelial tissue. The tumor has been named atypical teratoid/rhabdoid tumor (ATT/RhT) and is regarded as a unique class of primary central nervous system (CNS) tumors. It occurs most commonly in infants less than two years of age, has often metastasized throughout the CNS at presentation, does not respond to therapy and causes death less than a year after diagnosis. These tumors may occur in any CNS site but almost 60% are located in the cerebellum. The most common chromosomal abnormality involves chromosome 22.     

Atypical teratoid/rhabdoid tumour with leptomeningeal dissemination in an adult

Summary A 22-year-old man presented with a rare case of atypical teratoid/rhabdoid tumour (AT/RT). Magnetic resonance imaging showed a left cerebellar mass with leptomeningeal dissemination. Partial resection was performed. Histological examination revealed AT/RT. Postoperatively, whole neuraxis and local irradiation were performed. Three-drug chemotherapy with ifosfamide, cisplatin, and etoposide, and adjuvant intrathecal administration of methotrexate were repeated. Near complete response was achieved, and no tumour recurrence/progression has been noticed during the follow up of 24 months. Intensive radiochemotherapy can successfully control AT/RT, even with leptomeningeal dissemination.     

Importance of re-examination for medulloblastoma and atypical teratoid/rhabdoid tumor

Summary ¶Medulloblastoma may can be difficult to distinguish from atypical teratoid/rhabdoid tumor (AT/RT), since they resemble each other histologically. We re-examined whether AT/RT was included among cases who had been diagnosed as medulloblastoma.All of fifteen medulloblastomas (10 males and 5 females) diagnosed at the Kitasato University Hospital were collected and stained immunohistochemically.Two cases originally diagnosed as medulloblastoma were reclassified as AT/RT based on histological re-examination including immunohistochemical studies. While these two cases of AT/RT were found during infancy, only one medulloblastoma was found in infancy.Histologically, small rhabdoid cells and large, pale, bland cells were common but typical rhabdoid cells were not seen in the two AT/RTs. Gland-like structures were also seen. The tumor cells in AT/RT, but not those in medulloblastoma, were immunoreactive for vimentin, epithelial membrane antigen and smooth muscle actin. In conclusion, if a diagnosis of medulloblastoma is made histologically, it should be confirmed immunohistologically, since it is difficult to distinguish AT/RT from medulloblastoma. When appropriate treatment was specifically targeted at AT/RT it may improve the outcome.Published online July 23, 2003     

Atypical teratoid/rhabdoid tumour in sella turcica in an adult

Summary Although atypical teratoid rhabdoid tumours preferentially arise in the posterior fossa of infants, we encountered a 56 year old woman with an atypical teratoid rhabdoid tumour located in the sella. She presented with right abducent and oculomotor nerve paresis. Magnetic resonance imaging demonstrated an intrasellar tumour impinging on the right cavernous sinus. Microscopically, the tumour was composed of cells with rhabdoid features; we observed atypia, eccentric nuclei, and intracytoplasmic inclusion bodies. The Ki-67 labeling index was around 30%. The tumour cells were positive for vimentin, epithelial membrane antigen, and neurofilament, but negative for INI1. Despite extended local brain and whole-spine irradiation she died of neural axis dissemination. Correspondence: Kazunori Arita, M.D., Department of Neurosurgery, Graduate School of Medical and Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan.