Ectopic primary B cell lymphoma of the thyroid presenting as an anterior mediastinal mass. A case report.

Ectopic thyroid tumours arising in the mediastinum without connection to the cervical thyroid gland are very rare. Follicular adenoma, papillary carcinoma and follicular carcinoma in the mediastinum has been reported, but primary ectopic thyroid B cell lymphoma has not been reported previously. We report mediastinal primary ectopic thyroid large B cell lymphoma in an 80-year-old man. Differential diagnosis from primary mediastinal large B cell lymphoma and clinicopathologic features are discussed.