Introduction: Accessory thyroid tissue is a part of thyroid dysgenesis and sometime represents an incidental adult finding displaying a normal function.
Material and Methods: This is a case presentation of an adult admitted for an atypical anterior cervical aspect which could not be recognized as accessory thyroid tissue only after surgery. Thyroid evaluation used imagery like ultrasound, computed tomography (CT), assays as TSH (Thyroid Stimulating Hormone), calcitonin, TPO antibodies (anti-thyreoperoxidase).
Results: A 62-year male is diagnosed with prostate cancer at age of 58 and treated with radiotherapy and hormone blocking therapy with consecutive normalization of specific prostate antigen. His father was diagnosed and treated for bone cancer. While evaluation for his previous oncologic condition, CT scan with contrast revealed asymmetrical thyroid with a mass of unknown origin at the cervical lateral level, left to the esophagus, of oval shape with regular margins. The 2 centimeter sized mass causes a small deviation of the esophagus, and it has a hypo-dense spontaneous structure. Thyroid function was normal (TSH of 0.9 μUI/ml, N:0.54.5 μUI/ml), negative TPO and normal calcitonin and parathormone of 24.48 pg/ml (N:1565 pg/ml). A paraganglioma was suspected based on high circulating serotonin of 423 ng/ml (N:40400 ng/mll) but otherwise normal profile 24-h urinary metanephrines of 72 μg (N:50450 μg/24-h), and normetaneprines of 274 μg (N:100600 μg/24-h), plasma metanephrines of 29.6 pg/ml (N:1090 pg/ml), plasma normetanephrines of 82.2 pg/ml (N:15180 pg/ml), chromogranin A of 102 ng/ml (N:20125), neuron specific enolase of 9.13 ng/ml (N:012 ng/ml). The surgical removal was performed and thyroid tissue of adenomatous type was found. No malignancy, neither surrounding tissues were presented so a late diagnosis of thyroid dysgenesis was established.
Conclusion: Accessory thyroid tissue might not be highly suggestive at CT or ultrasound especially if the late diagnosis is done during adult years. The presence of a prior malignancy may require several imagery tests and consecutive discovery of the thyroid dysgenesia.