Primary adenoid cystic carcinoma of trachea presenting as midline neck swelling and mimicking thyroid tumor: A case report and review of literature.

We report an extremely rare case of primary adenoid cystic carcinoma (ACC) trachea presenting as midline swelling neck and mimicking thyroid tumor. A 44-year-old female presented with painless midline swelling neck without any respiratory complaints, hoarseness of voice or dysphagia etc. Fine needle aspiration cytology (FNAC) from swelling reveal features of papillary carcinoma thyroid. Subsequently the operative findings, bronchoscopy and histological diagnosis of excised mass, along with review of FNAC, revealed features of ACC of trachea with exra tracheal extension anteriorly into the soft tissue neck, without actual invasion of the thyroid gland. The world literature on extension of an ACC arising in the laryngotracheal complex to thyroid or soft tissue neck and clinical manifestation as a thyroid nodule or mass is reviewed. The cytological differential diagnosis of ACC and CT findings are also briefly discussed.