Atypical Teratoid Rhabdoid Tumor of the Third Cranial
Atypical Teratoid Rhabdoid Tumor of the Third Cranial Nerve (AT/RT) 1 R Clarke, 2 L Klesse, 3 B Braga, 4 V Rajaram, 1 K Koral University of Texas Southwestern Medical Center and Children's Health, Dallas, TX Departments of 1 Pediatric Radiology, 2 Oncology, 3 Neurosurgery and 4 Pathology Control #: 1168 Poster #: EE-29
Disclosures • The authors have nothing to disclose.
Purpose • AT/RT is a rare, aggressive tumor of the central nervous system – Once thought to represent a more aggressive type of primitive neuroectodermal tumor (PNET), now recognized as a completely separate entity by the World Health Organization since 2000. • Characteristic imaging features of AT/RT are well described, however, when found in uncommon locations these tumors can present difficulty in preoperative diagnosis. • We present this case to highlight that the differential diagnosis of an AT/RT involving the third cranial nerve is rather limited when its location, characteristic imaging features and patient's age are taken into consideration.
Material & Methods • Case Report: – Previously healthy 13 month-old girl seen by an ophthalmologist for 2 months of outward deviation of the left eye and drooping eyelid – On exam, found to have a left third cranial nerve palsy – MRI showed an enhancing mass in the interpeduncular fossa, related to the midbrain and hypothalamus. The cisternal segment of the left third cranial nerve could not be identified as a separate structure, unlike the normal right third cranial nerve
Imaging A, B: Axial T 2 (A) and postcontrast sagittal T 1 (B) images show a homogeneously enhancing, relatively T 2 hypointense lesion centered in the interpeduncular fossa, inseparable from the left cerebral peduncle.
Imaging C: Coronal reformatted balanced FFE image shows a normal right third cranial nerve (orange arrow) and the relatively T 2 hypointense mass (yellow arrows) in the expected location of the left third cranial nerve.
Imaging D: Axial diffusion-weighted image demonstrates peripheral regions of restricted diffusion (white arrows) within the tumor.
Results • The patient underwent stereotactic biopsy of the lesion, which was found to be an AT/RT • The patient is currently undergoing aggressive chemotherapy and conformal radiation therapy • Follow-up imaging at 7 months following initial diagnosis has demonstrated stability of the tumor
Conclusion • To our knowledge, there are only 4 previously reported cases of CN III AT/RT in the literature, all with striking similarities in both patient presentation and imaging findings • Our case is nearly identical to these • All reported cases of CN III AT/RT, including the present one, resemble AT/RTs found in other CNS locations
Conclusion • AT/RTs are WHO Grade IV tumors – Most often seen in the pediatric age group, most commonly presenting before the age of 3 years – Aggressive lesions with historically poor prognosis prior to the advent of more targeted therapies • Characteristic imaging features are those of a highly cellular malignant tumor – – Relatively iso- or hypointense T 2 signal Avid enhancement Restricted diffusion Features are highly consistent among AT/RTs found elsewhere in the CNS
Conclusion • Differential diagnosis for a tumor in this location – Cranial nerve schwannoma – Exophytic brainstem glioma • Both alternative diagnoses would demonstrate more T 2 hyperintensity and would not show restricted diffusion
Conclusion • Despite the still bleak prognosis for a child with AT/RT, timely initiation of appropriate treatment may serve to improve prognosis and prolong a patient’s life • Although rarely reported previously, AT/RT should be the leading diagnostic consideration of a tumor arising from a cranial nerve when characteristic imaging features and patient age are taken into consideration
References • Rorke LB, Packer RJ, Biegel JA: Central nervous system atypical teratoid/rhabdoid tumors of infancy and childhood: definition of an entity. J. Neurosurg 1996; 85: 56 -65. • Wykoff CC, Lam BL, Bratwaite CD, et al. Atypical Teratoid/Rhabdoid Tumor Arising From the Third Cranial Nerve. J Neuroophthalmol. 2008; 28(3): 207 – 211. • Oh CC, Orr BA, Bernardi B, et al. Atypical teratoid/rhabdoid tumor (ATRT) arising from the 3 rd cranial nerve in infants: a clinical-radiological entity? J Neurooncol 2015; 124: 175– 183
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