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E1179. Imaging a-PLNTY: Radiologic Features of the Polymorphous Low-Grade Neuroepithelial Tumour of the Young (PLNTY)
Authors
  1. Ashley Hastings-Robinson; University of California San Francisco
  2. Soonmee Cha; University of California San Francisco
Background
The polymorphous low-grade neuroepithelial tumour of the young (PLNTY) was first described as its own neurooncological entity in 2017 by Huse JT, Snuderl M, Jones DT, et al. as a brain tumour with oligodendroglioma-like components, aberrant CD34 expression, and genetic alterations in the MAP kinase pathway. The novelty of this tumour and its emergence through molecular genetic techniques have made it perhaps the least radiologically recognizable of the known epileptogenic brain tumours in children and young adults. The purpose of this exhibit is to explore the imaging features of this tumour and how these features may be used to differentiate it from other calcified epileptogenic brain tumours, using pathology proven cases from our institution.

Educational Goals / Teaching Points
We will present the 6 main imaging characteristics of the typical PLNTY, briefly highlight the pathologic features, present the 5 other brain tumour types it is most important to differentiate a suspected PLNTY from and, lastly, the main characteristics that can be used in differentiating PLNTY from each of the other tumours on our differential diagnosis. The PLNTY tumour characteristics, differential diagnosis, and key differentiating characteristics will be illustrated with imaging from pathology proven cases of all of these tumours from our institution.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Imaging Features of the Typical PLNTY: 1. Macroscopic calcification 2. Cystic component 3. Well-circumscribed margins 4. T1 post-contrast enhancement 5. Heterogeneity on both T1 and T2 weighted sequences 6. Temporal location Differential Diagnosis 1. Calcifying Pseudoneoplasm of the Neuraxis 2. Pilocytic Astrocytoma 3. Pleomorphic Xanthoastrocytoma 4. Ganglioglioma 5. Oligodendroglioma

Conclusion
PLNTY is an important etiology to be considered in a child or young adult presenting with an epileptogenic and/or calcified brain tumour. It is also perhaps the least familiar of all such tumours. We have presented 6 key imaging features of the typical PLNTY, the 5 other tumours that ought to be considered on the differential diagnosis when confronted with such a tumour at CT or MRI, and the imaging characteristics that can be used to engage in this differentiation process. Our hope is that this exhibit increases radiologists' comfort with proposing PLNTY as a diagnosis on the basis of brain imaging, and thereby improves the efficiency and accuracy with which these patients are diagnosed and treated on a broader scale.