Neuroendocrine tumors of the thymus.

Neuroendocrine tumors of the thymus (NETTs) are unusual thymic neoplasms that were misdiagnosed as thymomas until the 1970s, when they eventually acquired a distinct identity. No collective large series have been published so far, and information about clinical presentation, diagnosis, histology, and treatment is derived from analysis of the case series and case reports published over a long period. NETTs are more aggressive than their pulmonary and abdominal counterparts, presenting at a more advanced stage, often with distant metastases, and are associated with poor long-term survival. Most patients are symptomatic at presentation as a result of the local invasion. Twenty percent to 30% of the cases are associated with endocrine disorders, mostly Cushing syndrome and multiple endocrine neoplasia syndrome. There is no official staging system for these tumors and investigators rely on the Masaoka staging system used for thymomas. Histologically, 2 classification are used: the World Health Organization and the Armed Forces Institute of Pathology classifications. Histologically, most tumors show moderately to poorly differentiated histologic features, reflecting their aggressive clinical behavior. Surgery is the most effective treatment option, although the aggressiveness of the tumor often requires extensive resection. Chemotherapy and radiotherapy may be used either preoperatively or postoperatively, although the small number of patients does not allow the design of standard guidelines about optimal schedules and doses. Survival depends on stage at presentation, histologic degree of differentiation, associated endocrine syndromes, and resectability rate. Recurrences are frequent after surgery and may be locoregional or distant. Surgery is recommended when feasible in the treatment of locoregional recurrences.