Review ArticlesThymoma Staging: An Analysis of the Different SchemasMoran, Cesar A. MDAuthor Information Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX The author has no funding or conflicts of interest to disclose. Reprints: Cesar A. Moran, MD, Department of Pathology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030 (e-mail: [email protected]). All figures can be viewed online in color at www.anatomicpathology.com. Advances In Anatomic Pathology: September 2021 - Volume 28 - Issue 5 - p 298-306 doi: 10.1097/PAP.0000000000000315 Buy Metrics Abstract Over the last years, a number of changes has taken place in the evaluation of thymomas. More recently, the introduction of a TNM staging system in the assessment of thymic epithelial tumors, in general, has been put forward. Important to highlight is that this TNM system is not based on tumor size, and because of that shortcoming, it was in need to borrow most if not all of the information from the experience derived from other schemas that over the years have been tested with larger series of cases. Also important to recognize is that this TNM system is nothing new as previous authors in the past had already attempted to provide a TNM system for thymomas without much success. Therefore, it becomes important that those involved with the staging of thymomas become familiar with previous schemas as the TNM system provides a slight different spin in the T component, while the M component truly represents advance stages of previous schemas. More importantly is to also highlight that despite the specific anatomic structures addressed in the T or M assessment, there is little information in the most important aspect of any staging system—clear definitions of invasion and metastasis and the gross assessment of these tumors to provide an accurate staging. Capsular integrity still remains paramount in such assessment. A critical assessment of TNM system compared with previously proposed staging systems and whether there is a real advancement in applying it is discussed as well as the gross assessment of these tumors to highlight the importance of the staging protocol. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.