Intraoperative Consultations of Central Nervous System Tumors: A Review for Practicing Pathologists and Testing of an Algorithmic Approach

Abstract

Intraoperative consultations or frozen sections for central nervous system (CNS) tumors present a significant challenge for surgical pathologistsbecause of their relative rarity and diversity. Yet, such lesions are encountered by every surgical pathologist, and a basic understanding of clinical,radiological and genetic information is critical to successfully evaluate CNS frozen sections. It is often beneficial to have a systematic approachor an algorithm, and to be aware of the common pitfalls and mimickers when dealing with these lesions. We propose such an algorithm in aneffort to construct a sensible approach to CNS frozen sections that considers recent developments in the WHO CNS tumor classification. Thealgorithm was developed for surgical pathologists who are occasionally faced with making diagnosis of CNS tumors on frozen sections. To testthe algorithm and its practicability, we selected a group of tumors among a total of 3288 consecutive intraoperative consultations performed atUCSF between 2013 and 2017. The selected cases represented lesions that may be encountered in everyday surgical pathology and constituteda fair reflection of the main group. The algorithm was used by three of the authors who did not have formal neuropathology training and hadbeen in surgical pathology practice for at least 3 years. There was a very high level of concordance among the authors’ diagnosis (interobserverconcordance: 0.83-0.97-kappa value) using the algorithm with high intraobserver reliability (concordance 93%, p