Thymomas: Analysis of Histological Subtypes and Staging in Patients with Surgical Treatment in Two Reference Centers in Argentina

Abstract

Background: Thymomas are a heterogeneous group of tumors which represent the most frequent tumor of the anterior mediastinum. Aims: To describe the clinical, histological, surgical and oncological characteristics of a cohort of patients with a diagnosis of thymoma surgically treated in two centers in Argentina and to evaluate the possibility of retrospectively implementing the 8th edition of TNM staging. Materials and Methods: 180 patients with thymoma surgically treated over a period of 41 years were studied. The following variables were analysed: age, sex, presence of myasthenia gravis at diagnosis, Masaoka staging (1994), TNM staging of thymus tumors, Histological classification (WHO 2015), neoadjuvant treatment with chemotherapy, post-operative radiation treatment and clinical evolution of myasthenia gravis defined according to the modified Osserman classification. Results: 96 men and 84 women were analysed. Median age 51 years (range 13-85). 85% of the patients analysed came from the public sphere. When analysing the institutional distribution by Masaoaka-Koga stage and TNM, a higher proportion of stages I was observed for both staging systems. Most myasthenic patients belonged to the WHO B2 histological classification (49%, p=0.04) and 15 patients received neoadjuvant treatment prior to surgery to improve the chances of resection, most of them classified as stages III of Masaoka (p=0.002) or IIIa of the TNM stage (p=0.001). 74 (46%) cases received post-operative RT when they presented Masaoka Koga stages II (p=0.000) and IIIa or more advanced TNM staging (p=0.000). 76% of the patients presented remission or stability of symptoms after surgical treatment and only 3/6 died due to myasthenic crisis in the immediate post-operative period. Conclusion: As reported in the literature, we have observed a higher frequency of B2 thymomas and their association with Myasthenia gravis. The histological criteria of the WHO 2015 classification, based on the ITMIG recommendations, favour precision in the definition of subtypes. The retrospective implementation of the 8th edition of TNM staging highlights the need to standardize protocols for pathological and surgical studies.