Totally cervical thymoma from the orthotopic thymus.

Totally cervical thymoma is extremely rare and usually arises from ectopic thymic tissue. We report a case of a B1 thymoma localized in the neck, misdiagnosed for a decade as a thyroid nodule. Fine needle aspiration biopsy led to a preoperative suspicion of the correct diagnosis. The tumor was resected intact through a cervical collar incision, along with the upper thymic horn from which it originated. A pathogenetic hypothesis was formulated.