Clinicopathologic Characteristics, Treatment Outcomes, and Survival in Thymic Neuroendocrine Neoplasms (t-NEN): A 25-Year Single-Center Experience

<b>Background/Objectives</b>: Thymic neuroendocrine neoplasms (t-NENs) are rare, biologically aggressive malignancies of the anterior mediastinum. Due to their low incidence, clinical evidence remains limited, and treatment recommendations are primarily based on expert opinion and extrapolation from other neuroendocrine tumors. This study aimed to analyze the clinicopathological features, treatment patterns, and survival outcomes of patients with t-NENs treated at a single comprehensive cancer center over 25 years. <b>Methods</b>: A retrospective review was performed on 19 adult patients diagnosed with t-NENs between 2000 and 2024. Data on demographics, histology, treatment intent, modalities used, and outcomes were collected. Survival analyses-of overall survival (OS), disease-free survival (DFS) and progression-free survival (PFS)-were conducted using the Kaplan-Meier method. <b>Results</b>: The median age was 52 years; 63% of patients were male. Atypical carcinoid was the most common histologic subtype (52.6%), followed by large cell neuroendocrine carcinoma (31.6%). Paraneoplastic syndromes, including Cushing's syndrome, were observed in 26.3% of cases. Radical surgery was performed for 8 patients, but R0 resection was achieved in only 25% of them. Postoperative radiotherapy and chemotherapy were used for 36.8% and 15.8% of patients, respectively. Disease recurrence occurred in 44.4% of curatively treated patients. The median OS for the entire cohort was 127 months; patients treated with curative intent had a significantly longer OS (170 months) compared to those after palliative treatment (33 months). Median PFS in the palliative group was 11 months. <b>Conclusions</b>: t-NENs are aggressive tumors with high risk of recurrence and limited systemic treatment efficacy. Complete surgical resection remains the cornerstone of curative therapy. However, the overall prognosis remains poor, emphasizing the need for novel therapeutic strategies and prospective multicenter studies.