Primary Neuroendocrine Tumors of the Thymus: A Multicenter Experience of 35 Patients

Background. Primary neuroendocrine tumors of the thymus (NETT) are rare tumors and represent a distinct category of tumors collectively displaying morphologic and biological neuroendocrine features. We sought to evaluate factors influencing long-term survival in patients with primary NETT. Methods. From January 1990 to April 2011, 35 patients (27 male patients and 8 female patients) were surgically treated for primary NETT at 5 institutions. Results. No operative (30-day) mortality occurred. Morbidity was 37.14% (13/35 patients). All patients were followed for a total of 2,703 months. Fourteen patients had associated paraneoplastic syndrome. Twenty-four patients are alive, 19 of whom are free of disease and 5 of whom continue to have disease. The median overall survival was 153 months. The overall 5-year and 10-year actuarial survival rates were 84.34% and 60.82%, respectively. The 10-year survival was evaluated according to histologic type (typical carcinoid, 77.92%; atypical carcinoid, 54.55%; large-cell neuroendocrine carcinomas, 0%; Masaoka staging (stage I, 100%; stage II, 66.67%; stage III, 61.9%; stage Iva, 25%; stage IVb, 0%), presence of paraneoplastic syndrome (no = 70.67%; yes = 32.14%), postoperative radiotherapy (yes = 39.71%; no = 85.71.%), Surveillance, Epidemiology, and End Results (SEER) staging system (localized disease, 83.3%; regional disease, 53.3%; distant disease, 0%), tumor size (<7 cm = 90.9%; >= 7cm = 28.7%; p = 0.0007), and Ki67 expression, which was available in 23 patients (<10% = 85.71%; >= 10% = 0%; p = 0.0037). Conclusions. The prognosis of primary NETT is statistically significantly related to tumor size >7 cm and to the proliferation index (evaluated by Ki67 expression >10%). The histologic type of the neoplasm, the presence of a paraneoplastic syndrome, the Masaoka staging, the evidence of distant disease, and postoperative radiotherapy also impact prognosis.