Excerpta Extraordinaire Excerpta #:  EE-20 Imaging findings of Atypical Teratoid / Rhabdoid tumor in a 11-Year Old Boy H Nakamura1, T Suzuki1, M Uchida2, M Doi3, M Takagi3, Y Tanaka2, Y Nakajima2 , St. Marianna University of Medicine, Radiology1 and Neurodsurgery 2 and Pahtology3 Kawasaki Japan.

Disclosures The authors do not have a financial relationship with a commercial organization that may have a direct or indirect interest in the content.

Purpose Atypical teratoid / rhabdoid tumors (AT/RT) are rare aggressive neoplasms occurring in children younger than 2 years of age at the infratentorial. We demonstrate an atypical case of supratentorial AT/RT in a 11-year-old boy.

History . A 11-year-old boy came to our hospital complaining of mild headache and nausea, which had been continued for a month.

CT shows a large heterogeneous mass in the left frontal lobe, which contains two parts of iso density on the ventral side and low density on the dorsal side. Due to mass effect, ventricle , especially on the left side, is obliterated. Black arrow indicates small high density suggesting calcification. CT

DWI FLAIR

Axi / Cor T2 WI

T1WI Gd T1WI

Cor Gｄ T1WI Cor T2*

MRS

MRI findings Solid part (yellow arrow) - heterogeneous intensity on DWI, iso and high heterogeneous intensity on T2 WI and FLAIR , low and iso heterogeneous intensity on T1 WI and mild to moderate contrast enhancement on contrast images. MRS shows decreased NAA and prominent choline peak, suggesting cell membrane turn over. Necrotic or cystic part - low intensity on DWI and T1 WI, high signal on T2 WI, and no contrast enhancement Calcification and hemorrhage ( white arrow on T2*)

Imaging findings Large mass with solid and cystic component. Calcification and hemorrhage High choline peak.

Differential diagnosis Pilocytic astrocytoma Pleomorphic xanthoastrocytoma AT/RT Primitive Neuroectodermal Tumor (PNET) Glioma (glioblastoma, oligodendroglioma) (anaplastic ) ependymoma Desmoplastic infantile ganglioglioma/astrocytoma

Surgical findings Tumor shows well-defined margin Solid and cystic tumor Success of total removal

H&E stain Arrowなし H&E stain on high power shows　large pleomorphic cells with abundant eosinophilic cell and cells with large eccentrically located nucleus, which are characteristic of rhabdoid cells.

INI-1 stain immunohistochemistry stain for INI-1 on high power shows lack of staining (brown) in tumor cells with retention of staining in non-tumor cells.

Final Diagnosis Atypical Teratoid / Rhabdoid tumor (AT / RT)

AT/RT Highly malignant embryonal neoplasm (grade 4 according to the World Health Organization classification) that typically occurs in children aged <3 years and 6.7% of CNS neoplasm children aged < 3years1 Most often reported as infratentorial2, 3

Age and localization - our case Older than 10years -12%2, 9.1%3 Adult onset almost 30 cases were reported and they favor the supratentorial4 Some reports show supratentorial is more prevalent or comparative 2, 5

Pathology Characteristic “rhabdoid” phenotype ( large immature rhabdoid cells) are helpful for the diagnosis of AT/RT if present, however are not always seen. Pathologically , AT/RT has considerable overlap with medulloblastoma/PNET Cytogenetic evaluation of CNS AT/RT and renal AT/RT has revealed deletions and mutations of the INI1 locus in chromosome 22 INI1 thought to represent a tumor suppressor gene The immunohistochemical reagent for INI1 fails to stain the nuclei of tumor cells with INI1 mutations

Differential diagnosis Only imaging findings can not distinguish from other high-grade tumors Thick heterogeneous enhancing wall surrounding a central cyst or cysts is the key feature in differentiation from others6

Discussion The imaging feature is typical findings of AT/RT Supratentorial location and the age older 10 years are not typical, but not very rare

Conclusion When we see the supratentorial solid and cystic tumor even aged >10 years , differential diagnosis should include AT/RT

References 1. Buscariollo DL, Park HS, Roberts KB, et al. Survival outcomes in atypical teratoid rhabdoid tumor for patients undergoing radiotherapy in a Surveillance, Epidemiology, and End Results analysis. Cancer 2012;118:4212-4219 2. Meyers SP, Khademian ZP, Biegel JA, et al. Primary intracranial atypical teratoid/rhabdoid tumors of infancy and childhood: MRI features and patient outcomes. AJNR American journal of neuroradiology 2006;27:962-971 3. Warmuth-Metz M, Bison B, Dannemann-Stern E, et al. CT and MR imaging in atypical teratoid/rhabdoid tumors of the central nervous system. Neuroradiology 2008;50:447-452 4. Han L, Qiu Y, Xie C, et al. Atypical teratoid/rhabdoid tumors in adult patients: CT and MR imaging features. AJNR American journal of neuroradiology 2011;32:103-108 5. Jin B, Feng XY. MRI features of atypical teratoid/rhabdoid tumors in children. Pediatric radiology 2013;43:1001-1008 6. Au Yong KJ, Jaremko JL, Jans L, et al. How specific is the MRI appearance of supratentorial atypical teratoid rhabdoid tumors? Pediatric radiology 2013;43:347-354