The characteristics and prognostic role of thymic epithelial tumors with paraneoplastic autoimmune syndromes

Thymic epithelial tumors (TETs) are generally categorized as those that originate from thymic epithelial cells (thymoma and thymic carcinoma) and those that originate from neuroendocrine cells (thymic carcinoid, germ-cell tumor, and thymic cyst). Among the different types of TETs, this study specifically focused on thymoma, thymic cancer, and neuroendocrine tumors of the thymus (NETT) and examined the presence of paraneoplastic syndrome (PN/AI), specifically myasthenia gravis (MG), pure red cell aplasia (PRCA), and hypogammaglobulinemia, as comorbid autoimmune diseases (1). Padda et al. performed a retrospective analysis of patients with TETs and demonstrated that most patients had undergone surgical resection and 34% of those patients had PN/AI. The study is highly reliable as it used the largest database of TETs that is currently available in the world. However, as the authors state, MG was the most common PN/AI, with 96.5% (2,068/2,143) of patients with autoimmune syndromes having MG. In contrast, there were very few patients with PRCA and hypogammaglobulinemia, consisting of 2.2% and 0.6% of all patients with autoimmune syndromes, respectively. Thus, the study population mostly reflects the characteristics of those with TETs and TETs + MG, rather than TETs + PN/AI. Furthermore, 96.1% (2,061/2,143) of PN/AI (+) patients had thymoma while only 2.0% and 0.2% of PN/AI (+) patients had thymic cancer and NETT, respectively. Although the study did not compare the combinations of TETs with MG, PRCA, or hypogammaglobulinemia, the majority of patients likely were represented by those with thymoma or thymic cancer. Based on the WHO classification, Type B2 (37%) and Type AB (29.6%) thymomas were the most common in PN/AI (+) and PN/AI (–) patients, respectively. Based on pathological staging, 25.5% and 36.7% of patients in stage III or above had PN/AI (+) and PN/AI (–), respectively. Since most patients in advanced stages had PN/AI (–), the authors suggest that the symptoms associated with PN/AI enable early detection of TETs. The authors further performed multivariate analysis of clinical factors and demonstrated that PN/AI syndromes were associated with a younger age, type B1 thymoma, early-stage cancer, and increased rate of a complete resection status. They also examined the prognosis of patients and demonstrated that the presence of PN/AI syndromes was not independently associated with overall survival