Tracheal carcinoma presenting as a thyroid tumor.

Direct invasion of the trachea by an aggressive tumor originating in the thyroid gland is an unusual but well-documented phenomenon. The reverse situation, that is, a primary tracheal neoplasm invading by direct extension into the thyroid gland and presenting as a thyroid mass is apparently an even less common occurrence. A careful search of the literature has failed to reveal any recorded instances of this type of occurrence. We report a case of an adenoid cystic carcinoma arising in the trachea and invading the thyroid gland and recurrent laryngeal nerves causing vocal cord paralysis. The presentation of this lesion as a primary thyroid tumor is an unusual occurrence that serves to remind the clinician that in the differential diagnosis of thyroid masses one must include the possibilities of metastases or direct extension of a primary neoplasm from another organ.