Atypical Carcinoid of Thymus : Histologic Features

Neuroendocrine tumors of thymus are uncommon and make up 2% to 5% of all thymic neoplasms. The usual location is anterior mediastinum. The spectrum encountered in thymus is similar to that seen in the lungs and includes - typical carcinoid (low-grade), atypical carcinoid (intermediate grade), and small cell carcinoma and large cell neuroendocrine carcinoma (high-grade). Typical carcinoid and small cell carcinoma are seen more frequently in lungs, whereas thymic neuroendocrine tumors tend to be more often atypical carcinoids. Unlike in the lung, the thymic neuroendocrine tumors are not linked with smoking. They are all capable of recurrences, lymph node or distant metastases, and can cause death - with the greatest risk in the high-grade group.