Clinical presentation: A 54-year-old woman was referred for evaluation of a nodular goiter discovered by the patient one year ago. She noticed difficulties in swallowing.

Palpation: There were two firm nodules, one in the isthmus and another one in the left lobe.

Laboratory test: TSH 0.78 mIU/L.

Ultrasonography. There was an echonormal-cystic nodule in the right lobe. The left was composed of a large hypoechogenic nodule. The lesion presented abutment at the medial and the at the dorsal part. The borders of the lesion were lobulated. There were a few punctate echogenic foci within the lesion. The nodule presented intranodular vascularization.

Cytology was performed from the hypoechoic nodule and resulted in suspicion of carcinoma.

Serum calcitonin was 0.59 pM/l while wash-out thyroglobulin level resulted in 4 ug/L. On these results, a medullary carcinoma could be excluded and the likelihood of a primary thyroid carcinoma of follicular-cell origin was very low.

Our final diagnosis was suspicion of carcinoma, either an oxyphilic tumor or a secondary cancer.

Histopathology disclosed a T4b parathyroid carcinoma which broke into the trachea.

Comment.

1. The ultrasound presentation of a tumor breaking into the trachea lack two of the three possible findings of the usual ultrasound signs: the capsule usually lacks at the medial of the thyroid and bulging cannot be visualized - both because of the acoustic shadow caused by the cartilage of the trachea.
   
2. Parathyroid carcinoma is a rare finding. In our practice two cases have occurred during more than 25 years. (It is worth comparing this number to the 30 cases of secondary thyroid carcinomas which has been diagnosed by ourselves.)