Abstract
Primary posterior fossa tumors comprise a large group of neoplasias with variable aggressiveness and short and long-term outcomes. This study aimed to validate the clinical usefulness of a radiologic decision flow chart based on previously published neuroradiologic knowledge for the diagnosis of posterior fossa tumors in children. A retrospective study was conducted (from January 2013 to October 2019) at 2 pediatric referral centers, Children's Hospital of Philadelphia, United States, and Great Ormond Street Hospital, United Kingdom. Inclusion criteria were younger than 18 years of age and histologically and molecularly confirmed posterior fossa tumors. Subjects with no available preoperative MR imaging and tumors located primarily in the brain stem were excluded. Imaging characteristics of the tumors were evaluated following a predesigned, step-by-step flow chart. Agreement between readers was tested with the Cohen κ, and each diagnosis was analyzed for accuracy. A total of 148 cases were included, with a median age of 3.4 years (interquartile range, 2.1-6.1 years), and a male/female ratio of 1.24. The predesigned flow chart facilitated identification of pilocytic astrocytoma, ependymoma, and medulloblastoma sonic hedgehog tumors with high sensitivity and specificity. On the basis of the results, the flow chart was adjusted so that it would also be able to better discriminate atypical teratoid/rhabdoid tumors and medulloblastoma groups 3 or 4 (sensitivity = 75%-79%; specificity = 92%-99%). Moreover, our adjusted flow chart was useful in ruling out ependymoma, pilocytic astrocytomas, and medulloblastoma sonic hedgehog tumors. The modified flow chart offers a structured tool to aid in the adjunct diagnosis of pediatric posterior fossa tumors. Our results also establish a useful starting point for prospective clinical studies and for the development of automated algorithms, which may provide precise and adequate diagnostic tools for these tumors in clinical practice.
Highlights
In the last 10 years, there has been an exponential increase in knowledge of the molecular characteristics of pediatric brain tumors, which was only partially incorporated in the 2016 World Health Organization (WHO) Classification of Tumors of the Central Nervous System[1]
The fact that tumors with similar histological appearances can be related to completely different cellular populations, with different molecular profiles and different embryological origins, implies that they develop along different cellular paths
In light of the crucial role of molecular profiling in tumor diagnosis and management, we found that the pre-designed flowchart was very useful for categorizing and better understanding pediatric brain tumors
Summary
In the last 10 years, there has been an exponential increase in knowledge of the molecular characteristics of pediatric brain tumors, which was only partially incorporated in the 2016 World Health Organization (WHO) Classification of Tumors of the Central Nervous System[1]. A typical example is the four main groups of medulloblastoma: wingless (WNT), sonic hedgehog (SHH) with or without p53 mutation, group 3, and group 4. Though they may appear similar on microscopy, these categories have distinct molecular profiles, epidemiology, prognosis, and embryological origin[3]. MRI shows promise as a modality for differentiating histological tumors and their molecular subgroups. This capability relies on various imaging characteristics, and on location and spatial extension of the tumor, evident on MRI, which can be traced to the embryological origin of the neoplastic cells[5,7,8,9,10]
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