Atypical presentation of an atypical carcinoid.

Carcinoids are malignant neuroendocrine tumors consisting of a spectrum of neoplasms from low-grade typical carcinoid to high-grade small cell carcinoma. Primary neuroendocrine lesions in the mediastinum, especially the thymic region, are rare. Therefore, presently no uniform criteria are available for diagnosis, staging, risk assessment, and treatment. Generally, carcinoid tumors are indolent. However, when they occur in the thymic region, these tumors should be considered as aggressive neoplasms with an elevated risk of local recurrence and distant metastases.