Adenoid cystic carcinoma of the external auditory canal with metastases to lymph nodes and lungs--problematic diagnosis and treatment based on a case report.

Adenoid cystic carcinoma (ACC) of the external auditory canal (EAC) is an exceedingly rare tumor. Despite the slow growth it is characterized by a high malignancy and infiltration of surrounding tissue. Differential diagnosis may be especially difficult if the tumor appears in an atypical localization as it can present with non-specific features. The optimal treatment of this malignancy has not been fully established. We present a case report of a 55-year-old man with ACC of EAC metastasizing to the lymph nodes, lungs and vertebrae, with intracranial involvement. The patient was initially diagnosed with basal cell carcinoma (BCC) of EAC based on MR imaging examinations and excisional biopsy from EAC. Current information about nomenclature, epidemiology, characteristic features and treatment possibilities of ACC are presented and difficulties in making diagnosis are discussed. ACC should be considered among the malignant tumors of EAC. Its natural behavior is probably more unpredictable than commonly thought. Similar cases are rare and our knowledge about the tumor's specificity and prognosis is limited.