Clinical presentation: A 41-year-old woman was referred for aspiration cytology. She was evaluated of progressive bone pains and repeated nephrolithiasis. Elevated parathormone and serum calcium levels and a nodule in the region of the left thyroid lobe were found.

Palpation: A hard nodule was palpable in the lower pole of the left lobe.

Laboratory tests: serum-calcium 2.91 mM/L, parathormone 194 ng/mL (normal value: 10-65) and euthyroidism. 

Ultrasonography. There was a deeply hypoechogenic lesion dorsal and lateral to the lower pole of the left lobe. The vascularization was increased. 

Preliminary cytology diagnosis: atypical follicular tumor of the thyroid or parathyroid tumor.

Wash-out thyroglobulin level was lower than 0,1 ng/ml.

Other tests: serum calcitonin level was in the normal range. Neck and upper mediastinal CT-scan revealed enlarged lymph nodes in the upper part of the mediastinum.

Histopathology: parathyroid carcinoma with metastases to the neck and mediastinal lymph nodes.

Comments.

1. The location of the lesion had to raise the possibility of parathyroid origin.

2. As in most cases of parathyroid tumors the cytological pattern is practically identical with that of a thyroid follicular tumor.

3. Parathyroid carcinoma is a very rare tumor accounting for 0.1% to 5.0% of all cases of primary hyperparathyroidism. It is not only not a cytological diagnosis but even not a preoperative diagnosis.

4. The wash-out technique may be of great help in non-thyroidal lesions.